Add sort-alternatives rule (#235)

* WIP

* WIP

* Update to `[email protected]`

* Improved sorting for numbers

* Minor refactoring

* Finished work

* Allow apostrophes

* Added docs

* Updated compare function

Author: RunDevelopment

README.md

@@ -148,6 +148,7 @@ The rules with the following star :star: are included in the `plugin:regexp/reco
 | [regexp/prefer-range](https://ota-meshi.github.io/eslint-plugin-regexp/rules/prefer-range.html) | enforce using character class range | :wrench: |
 | [regexp/prefer-regexp-exec](https://ota-meshi.github.io/eslint-plugin-regexp/rules/prefer-regexp-exec.html) | enforce that `RegExp#exec` is used instead of `String#match` if no global flag is provided |  |
 | [regexp/prefer-regexp-test](https://ota-meshi.github.io/eslint-plugin-regexp/rules/prefer-regexp-test.html) | enforce that `RegExp#test` is used instead of `String#match` and `RegExp#exec` | :wrench: |
+| [regexp/sort-alternatives](https://ota-meshi.github.io/eslint-plugin-regexp/rules/sort-alternatives.html) | sort alternatives if order doesn't matter | :wrench: |
 
 ### Stylistic Issues
 

docs/rules/README.md

@@ -62,6 +62,7 @@ The rules with the following star :star: are included in the `plugin:regexp/reco
 | [regexp/prefer-range](./prefer-range.md) | enforce using character class range | :wrench: |
 | [regexp/prefer-regexp-exec](./prefer-regexp-exec.md) | enforce that `RegExp#exec` is used instead of `String#match` if no global flag is provided |  |
 | [regexp/prefer-regexp-test](./prefer-regexp-test.md) | enforce that `RegExp#test` is used instead of `String#match` and `RegExp#exec` | :wrench: |
+| [regexp/sort-alternatives](./sort-alternatives.md) | sort alternatives if order doesn't matter | :wrench: |
 
 ### Stylistic Issues
 

docs/rules/sort-alternatives.md

@@ -0,0 +1,46 @@
+---
+pageClass: "rule-details"
+sidebarDepth: 0
+title: "regexp/sort-alternatives"
+description: "sort alternatives if order doesn't matter"
+---
+# regexp/sort-alternatives
+
+> sort alternatives if order doesn't matter
+
+- :exclamation: <badge text="This rule has not been released yet." vertical="middle" type="error"> ***This rule has not been released yet.*** </badge>
+- :wrench: The `--fix` option on the [command line](https://eslint.org/docs/user-guide/command-line-interface#fixing-problems) can automatically fix some of the problems reported by this rule.
+
+## :book: Rule Details
+
+This rule will sort alternatives to improve readability and maintainability.
+
+The primary target of this rule are lists of words and/or numbers. These lists are somewhat common and sorting them makes it easy for readers to check whether a particular word or number is included.
+
+This rule will only sort alternatives if reordering the alternatives doesn't affect the pattern.
+
+<eslint-code-block fix>
+
+```js
+/* eslint regexp/sort-alternatives: "error" */
+
+/* ✓ GOOD */
+var foo = /\b(1|2|3)\b/;
+var foo = /\b(alpha|beta|gamma)\b/;
+
+/* ✗ BAD */
+var foo = /\b(2|1|3)\b/;
+var foo = /__(?:Foo|Bar)__/;
+var foo = /\((?:TM|R|C)\)/;
+```
+
+</eslint-code-block>
+
+## :wrench: Options
+
+Nothing.
+
+## :mag: Implementation
+
+- [Rule source](https://github.com/ota-meshi/eslint-plugin-regexp/blob/master/lib/rules/sort-alternatives.ts)
+- [Test source](https://github.com/ota-meshi/eslint-plugin-regexp/blob/master/tests/lib/rules/sort-alternatives.ts)