Parser: Mention strict: false in OmittedClosingTagError message (#1189)

```diff
- Element `<%s>` at (%u:%u) has its closing tag omitted. While valid HTML, consider adding an explicit `</%s>` closing tag at (%u:%u) for clarity.
+ Element `<%s>` at (%u:%u) has its closing tag omitted. While valid HTML, consider adding an explicit `</%s>` closing tag at (%u:%u) for clarity, or set `strict: false` to allow this.
```

Author: marcoroth

config.yml

@@ -231,7 +231,7 @@ errors:
 
     - name: OmittedClosingTagError
       message:
-        template: "Element `<%s>` at (%u:%u) has its closing tag omitted. While valid HTML, consider adding an explicit `</%s>` closing tag at (%u:%u) for clarity."
+        template: "Element `<%s>` at (%u:%u) has its closing tag omitted. While valid HTML, consider adding an explicit `</%s>` closing tag at (%u:%u) for clarity, or set `strict: false` to allow this."
         arguments:
           - opening_tag->value
           - opening_tag->location.start.line

javascript/packages/linter/test/rules/parser-no-errors.test.ts

@@ -27,7 +27,7 @@ describe("ParserNoErrorsRule", () => {
   })
 
   test("should report errors for unclosed elements", () => {
-    expectError("Element `<p>` at (2:3) has its closing tag omitted. While valid HTML, consider adding an explicit `</p>` closing tag at (3:0) for clarity. (`OMITTED_CLOSING_TAG_ERROR`)")
+    expectError("Element `<p>` at (2:3) has its closing tag omitted. While valid HTML, consider adding an explicit `</p>` closing tag at (3:0) for clarity, or set `strict: false` to allow this. (`OMITTED_CLOSING_TAG_ERROR`)")
 
     assertOffenses(dedent`
       <div>
@@ -61,7 +61,7 @@ describe("ParserNoErrorsRule", () => {
 
   test("should report multiple parser errors", () => {
     expectError("Opening tag `<h2>` at (1:1) doesn't have a matching closing tag `</h2>` in the same scope. (`MISSING_CLOSING_TAG_ERROR`)")
-    expectError("Element `<p>` at (2:3) has its closing tag omitted. While valid HTML, consider adding an explicit `</p>` closing tag at (4:0) for clarity. (`OMITTED_CLOSING_TAG_ERROR`)")
+    expectError("Element `<p>` at (2:3) has its closing tag omitted. While valid HTML, consider adding an explicit `</p>` closing tag at (4:0) for clarity, or set `strict: false` to allow this. (`OMITTED_CLOSING_TAG_ERROR`)")
     expectError("Found closing tag `</h3>` at (3:2) without a matching opening tag in the same scope. (`MISSING_OPENING_TAG_ERROR`)")
     expectError("Found closing tag `</div>` at (4:2) without a matching opening tag in the same scope. (`MISSING_OPENING_TAG_ERROR`)")