refactor!: drop support for <sub> and <sup> syntax

BREAKING CHANGE: special Markdown syntax to handle
<sub> and <sup> tags is now deprecated. Please use
the HTML tags instead directly in Markdown document.

Author: bandantonio

README.md

@@ -19,8 +19,6 @@ The main idea behind creating Antmarky was to have a generator with *zero config
     * Images with inline dimensions attributes
     * Reference links
     * Strikethrough
-    * Subscript
-    * Superscript
     * Tables
 * [Admonitions][admonitions]
 * [Syntax highlighting][syntax-highlight]

docs/markdown.md

@@ -7,8 +7,6 @@ Antmarky uses `GitHub` flavor for the Markdown parser. The parser supports the f
 * [Images with inline dimensions attributes](#image-dimensions)
 * [Reference links](#reference-links)
 * [Strikethrough](#strikethrough)
-* [Subscript](#subscript)
-* [Superscript](#superscript)
 * [Tables](#tables)
 
 ## Heading ids
@@ -55,22 +53,6 @@ a ~~strikethrough~~ element
 
 a ~~strikethrough~~ element
 
-## Subscript
-
-```md
-H~2~O
-```
-
-H~2~O
-
-## Superscript
-
-```md
-x^2^ * y^2^
-```
-
-x^2^ * y^2^
-
 ## Tables
 
 ```md

src/extensions/text-modifications.js

@@ -24,18 +24,6 @@ let markyText = (text) => {
       regex: /<pre><code>/g,
       replace: '<pre data-language="text"><code>'
     },
-    // SUBSCRIPT
-    {
-      type: 'output',
-      regex: /~(\d{1})~/g,
-      replace: '<sub>$1</sub>'
-    },
-    // SUPERSCRIPT
-    {
-      type: 'output',
-      regex: /\^(\d|\w)\^/g,
-      replace: '<sup>$1</sup>'
-    },
     // TABLE
     { 
       type: 'output',