Git Hook: lint-staged (#18)

Git Hooks [1] are a fantastic way to customize the development workflow
of a project to simplify and automate specific tasks that are required
when working on the code base. For example, this includes tasks like
formatting, "linting" and running tests before pushing a commit to
ensure it conforms to the code style and works as expected.
Most Git Hooks are not that complex and fullfil a simple purpose while
other solutions like Danger [2] can help to manage larger projects and
projects that need to scale.

This "base" repository template initially uses a Git Hook that
automatically runs configured linters on all files that have been staged
and that match the configured pattern (file extension, filename etc.).
Like documented in GH-15, NodeJS [3] is already a development dependency
anyway so the lint-staged [4] NPM package is used for this goal.
I've used this package in almost any project and it's again the most
stable, production-proven and advanced tool that is currently out there
with no comparable alternatives in other languages.

>>> Configuration

The configuration file `lint-staged.config.js` is placed in the project
root and includes the command that should be run for matching file
extensions (globs). Initialliy it includes the following three entries
with the same order as listed here:

1. `prettier --check` - Runs Prettier [5] (GH-13)
   to ensure all files are formatted correctly.
   The `--list-different` prints files that are not conform with the
   Prettier configuration.
2. `remark --no-stdout` - Runs remark-lint [6] (GH-15) against `*.md` to
   ensure all Markdown files are compliant to the style guide.
   The `--no-stdout` flag suppresses the output of the parsed file
   content.

[1]: https://git-scm.com/book/en/v2/Customizing-Git-Git-Hooks
[2]: https://danger.systems
[3]: https://nodejs.org
[4]: https://github.com/okonet/lint-staged
[5]: https://prettier.io
[6]: https://github.com/remarkjs/remark-lint

Closes GH-17

lint-staged.config.js

@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) 2020-present Sven Greb <[email protected]>
+ * This source code is licensed under the MIT license found in the LICENSE file.
+ */
+
+/**
+ * The configuration for lint-staged.
+ *
+ * @see https://github.com/okonet/lint-staged#configuration
+ */
+module.exports = {
+  "*": "prettier --check",
+  "*.md": "remark --no-stdout",
+};

package.json

@@ -25,6 +25,7 @@
     "lint:pretty": "prettier --check ."
   },
   "devDependencies": {
+    "lint-staged": "^10.2.11",
     "npm-run-all": "^4.1.5",
     "prettier": "^2.0.5",
     "remark-preset-lint-arcticicestudio": ">=0.3.0 <1.0.0"