refine the changelog text and highlight nil (#71)

##### Objective
To prepare releasing the version 1.4.0, I want to update the change log text reviewed by our User Assistance.

##### Abstractions
I also fix a TODO item in the codes for localization missing. After fixed it in CI you may see some gulp complaints. This is expected, and it will be fixed after I updated the localization strings:
```
[17:20:04] [i18n] Generating localized messages for 'ptb' resulted in the following problems:
[17:20:04] [i18n]
[17:20:04] [i18n] No localized message found for key autolispext.regionsnippet.title
[17:20:04] [i18n] No localized message found for key autolispext.project.closeproject.title
[17:20:04] [i18n]
```
I also add the nil to the highlight keyword.

##### Tests performed
 - markdown preview the change log text
 - highlight the nil text

##### Screen shot

![image](https://user-images.githubusercontent.com/68938334/105928048-2d7a4400-6080-11eb-9604-f70cb55b277a.png)

Author: hualin-wu-2000

CHANGELOG.md

@@ -1,8 +1,11 @@
 ## [1.4.0] - 2021-01-20
-a. Added Right Click -> 'Open Online Help' feature. This makes it possible for users to quickly access official documentation on a selected symbol.
-b. Support to insert custom regions.
-c. F12 "Go to definition" support.
-d. Fix DCL comments issue and other minor bugs.
+a.	Added the ability to open the reference documentation of a built-in function or DCL tile/attribute when a LSP or DCL file is open. Select a function or DCL tile/attribute, and then right-click and choose "Open Online Help" to open the associated reference documentation.
+
+b.	Added support to insert user-defined regions. A region is defined using the ;#region and ;#endregion comments.
+
+c.	Added support to go to the definition of a user-defined function or variable. Select a user-defined function or variable, and then press F12 to use the "Go to Definition" feature.
+
+d.	Fixed an issue with DCL comments and some other minor issues.
 
 ## [1.3.2] - 2020-12-17
 Remove the call to the deprecated vscode APIs

extension/src/project/findReplace/options.ts

@@ -1,6 +1,7 @@
 import * as vscode from 'vscode';
 import { optionButton } from './optionButton';
 import { IconUris } from '../icons';
+import { AutoLispExt } from '../../extension';
 
 export class SearchOption {
     static activeInstance: SearchOption = new SearchOption;//the one bound to search UI
@@ -107,9 +108,7 @@ export async function getString(title: string, hint: string) {
             quickpick.value = '';
             quickpick.ignoreFocusOut = true;
 
-            // TODO: do localization latter, now it has no enu\out\project\findReplace\options.i18n.json
-            //let closeTooltip = AutoLispExt.localize("autolispext.project.findreplace.optionbutton.close", "Close");
-            let closeTooltip = "Close";
+            let closeTooltip = AutoLispExt.localize("autolispext.project.findreplace.optionbutton.close", "Close");
             let closeBtn = new optionButton(IconUris.closeUri(), null, true, closeTooltip, optionButton.name_Close);
             quickpick.buttons = [closeBtn];
 

extension/syntaxes/autolisp.tmLanguage.json

@@ -76,7 +76,7 @@
 					"match": "(?<=\\(|\\[|'|\\s|^)(?i:1\\+|1-|\\*error\\*|\\*last-value\\*|\\*merr\\*|\\*merrmsg\\*|\\*pop-error-mode\\*|\\*push-error-using-command\\*|\\*push-error-using-stack\\*|\\*start\\*)(?=\\]|\\s|\\)|\\()"
 				},{
 					"name": "keyword",
-					"match": "(?<=\\(|\\[|'|\\s|^)(?i:VLISP-COMPILE|_VER|C:VLDEBUG|C:VLIDE|_vl-balance-parenthesis)(?=\\]|\\s|\\)|\\()"
+					"match": "(?<=\\(|\\[|'|\\s|^)(?i:VLISP-COMPILE|_VER|C:VLDEBUG|C:VLIDE|_vl-balance-parenthesis|nil)(?=\\]|\\s|\\)|\\()"
 				},{
 					"name": "keyword",
 					"match": "(?<=\\(|\\[|'|\\s|^)(?i::constants-prefix|:methods-prefix|:prog-id|:properties-prefix|:tlb-filename|:vlax-false|:vlax-null|:vlax-true|:vlr-abortattach|:vlr-abortdeepclone|:vlr-abortdxfin|:vlr-abortdxfout|:vlr-abortinsert|:vlr-abortrestore|:vlr-abortwblock|:vlr-acdb-reactor|:vlr-beginattach|:vlr-beginclose|:vlr-begindeepclone|:vlr-begindeepclonexlation|:vlr-begindoubleclick|:vlr-begindwgopen|:vlr-begindxfin|:vlr-begindxfout|:vlr-begininsert|:vlr-begininsertm|:vlr-beginrestore|:vlr-beginrightclick|:vlr-beginsave|:vlr-beginwblock|:vlr-beginwblockid|:vlr-beginwblockobjects|:vlr-beginwblockpt|:vlr-cancelled|:vlr-comandeered|:vlr-command-reactor|:vlr-commandcancelled|:vlr-commandended|:vlr-commandfailed|:vlr-commandwillstart|:vlr-copied|:vlr-databaseconstructed|:vlr-databasetobedestroyed|:vlr-deepclone-reactor|:vlr-docframemovedorresized|:vlr-docmanager-reactor|:vlr-documentbecamecurrent|:vlr-documentcreated|:vlr-documentlockmodechanged|:vlr-documentlockmodechangevetoed|:vlr-documentlockmodewillchange|:vlr-documenttobeactivated|:vlr-documenttobedeactivated|:vlr-documenttobedestroyed|:vlr-dwg-reactor|:vlr-dwgfileopened|:vlr-dxf-reactor|:vlr-dxfincomplete|:vlr-dxfoutcomplete|:vlr-editor-reactor|:vlr-endattach|:vlr-enddeepclone|:vlr-enddwgopen|:vlr-endinsert|:vlr-endrestore|:vlr-endwblock|:vlr-erased|:vlr-goodbye|:vlr-insert-reactor|:vlr-layoutswitched|:vlr-linker-reactor|:vlr-lisp-reactor|:vlr-lispcancelled|:vlr-lispended|:vlr-lispwillstart|:vlr-mainframemovedorresized|:vlr-miscellaneous-reactor|:vlr-modified|:vlr-modifiedxdata|:vlr-modifyundone|:vlr-mouse-reactor|:vlr-object-reactor|:vlr-objectappended|:vlr-objectclosed|:vlr-objecterased|:vlr-objectmodified|:vlr-objectopenedformodify|:vlr-objectreappended|:vlr-objectunappended|:vlr-objectunerased|:vlr-openedformodify|:vlr-otherattach|:vlr-otherinsert|:vlr-otherwblock|:vlr-pickfirstmodified|:vlr-reappended|:vlr-redirected|:vlr-rxapploaded|:vlr-rxappunloaded|:vlr-savecomplete|:vlr-subobjmodified|:vlr-sysvar-reactor|:vlr-sysvarchanged|:vlr-sysvarwillchange|:vlr-toolbar-reactor|:vlr-toolbarbitmapsizechanged|:vlr-toolbarbitmapsizewillchange|:vlr-unappended|:vlr-undo-reactor|:vlr-undosubcommandauto|:vlr-undosubcommandback|:vlr-undosubcommandbegin|:vlr-undosubcommandcontrol|:vlr-undosubcommandend|:vlr-undosubcommandmark|:vlr-undosubcommandnumber|:vlr-unerased|:vlr-unknowncommand|:vlr-wblock-reactor|:vlr-wblocknotice|:vlr-window-reactor|:vlr-xref-reactor|:vlr-xrefsubcommandattachitem|:vlr-xrefsubcommandbinditem|:vlr-xrefsubcommanddetachitem|:vlr-xrefsubcommandoverlayitem|:vlr-xrefsubcommandpathitem|:vlr-xrefsubcommandreloaditem|:vlr-xrefsubcommandunloaditem)(?=\\]|\\s|\\)|\\()"