docs(eslint-plugin): add prefer-includes to readme (#450)

packages/eslint-plugin/README.md

@@ -149,6 +149,7 @@ Then you should add `airbnb` (or `airbnb-base`) to your `extends` section of `.e
 | [`@typescript-eslint/no-var-requires`](./docs/rules/no-var-requires.md)                                   | Disallows the use of require statements except in import statements (`no-var-requires` from TSLint)                                                 | :heavy_check_mark: |          |                   |
 | [`@typescript-eslint/prefer-for-of`](./docs/rules/prefer-for-of.md)                                       | Prefer a ‘for-of’ loop over a standard ‘for’ loop if the index is only used to access the array being iterated.                                     |                    |          |                   |
 | [`@typescript-eslint/prefer-function-type`](./docs/rules/prefer-function-type.md)                         | Use function types instead of interfaces with call signatures (`callable-types` from TSLint)                                                        |                    | :wrench: |                   |
+| [`@typescript-eslint/prefer-includes`](./docs/rules/prefer-includes.md)                                   | Enforce `includes` method over `indexOf` method.                                                                                                    |                    | :wrench: | :thought_balloon: |
 | [`@typescript-eslint/prefer-interface`](./docs/rules/prefer-interface.md)                                 | Prefer an interface declaration over a type literal (type T = { ... }) (`interface-over-type-literal` from TSLint)                                  | :heavy_check_mark: | :wrench: |                   |
 | [`@typescript-eslint/prefer-namespace-keyword`](./docs/rules/prefer-namespace-keyword.md)                 | Require the use of the `namespace` keyword instead of the `module` keyword to declare custom TypeScript modules. (`no-internal-module` from TSLint) | :heavy_check_mark: | :wrench: |                   |
 | [`@typescript-eslint/promise-function-async`](./docs/rules/promise-function-async.md)                     | Requires any function or method that returns a Promise to be marked async. (`promise-function-async` from TSLint)                                   |                    |          | :thought_balloon: |