docs: Add links to opinion rules

lib/rules/opinions.js

@@ -7,13 +7,30 @@
  * If it can't be --fix'ed, it doesn't belong in here.
  */
 module.exports = {
+  /**
+   * Everything reported by prettier will be fixed by prettier.
+   *
+   * See: https://github.com/prettier/eslint-plugin-prettier
+   */
   'prettier/prettier': [
     'error',
     {
       singleQuote: true,
       trailingComma: 'es5',
     },
   ],
+
+  /**
+   * After 'use strict' there's a newline.
+   *
+   * See: https://eslint.org/docs/rules/lines-around-directive
+   */
   'lines-around-directive': ['error', 'always'],
+
+  /**
+   * After the last require/import statement, there's a newline.
+   *
+   * See: https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/newline-after-import.md
+   */
   'import/newline-after-import': 'error',
 };