fix(eslint-typescript): add missing optional ruleset

Author: robertrossmann

packages/eslint-config-typescript/optional.js

@@ -0,0 +1,14 @@
+/**
+ * strvcom/eslint-config-typescript
+ *
+ * @author      Robert Rossmann <rr.rossmann@me.com>
+ * @copyright   2019 STRV
+ * @license     http://choosealicense.com/licenses/bsd-3-clause  BSD-3-Clause License
+ */
+
+'use strict'
+
+module.exports = {
+
+  extends: require.resolve('@strv/eslint-config-base/optional'),
+}

packages/eslint-config-typescript/readme.md

@@ -15,6 +15,20 @@ In addition to using this ruleset, you should also choose one base ruleset depen
 - [`@strv/eslint-config-node`][eslint-config-node]
 - [`@strv/eslint-config-react`][eslint-config-react]
 
+## Optional configurations
+
+### `@strv/eslint-config-node/optional`
+
+Use this ruleset in conjunction with any of the above version-specific rulesets. Provides additional insights into potential inconsistencies in the project.
+
+> For new projects, it is recommended to enable this ruleset. For existing projects, it is only recommended for the brave.
+
+## Coding styles
+
+### `@strv/eslint-config-typescript/style`
+
+This ruleset includes rules which deal with how the code looks like and not how it works. It helps keeping the code clean and consistent. 🎨
+
 A full configuration for a TypeScript on Node.js project:
 
 ```js
@@ -38,12 +52,6 @@ To actually lint .ts files, you must pass the `--ext` flag to ESLint:
 eslint --ext ts --no-unused-disable-directives .
 ```
 
-## Coding styles
-
-### `@strv/eslint-config-typescript/style`
-
-This ruleset includes rules which deal with how the code looks like and not how it works. It helps keeping the code clean and consistent. 🎨
-
 ## License
 
 See the [LICENSE](LICENSE) file for information.