feat: Adjust commitlint config for our standards

Our standards differ from the "conventional" config by the following:

 * We allow the subject to be anything but upper case
 * We allow kebab case scope (Well...)
 * By default, we do not allow scopes
 * We allow a max line length of 90 characters for the body and footer

commitlint.js

@@ -3,13 +3,16 @@
 module.exports = {
    rules: {
       'body-leading-blank': [ 2, 'always' ],
+      'body-max-line-length': [ 2, 'always', 90 ],
       'footer-leading-blank': [ 2, 'always' ],
+      'footer-max-line-length': [ 2, 'always', 90 ],
       'header-max-length': [ 2, 'always', 72 ],
-      'scope-case': [ 2, 'always', 'lower-case' ],
+      'scope-case': [ 2, 'always', [ 'lower-case', 'kebab-case' ] ],
+      'scope-empty': [ 2, 'always' ],
       'subject-case': [
          2,
          'never',
-         [ 'sentence-case', 'start-case', 'pascal-case', 'upper-case' ],
+         [ 'upper-case' ],
       ],
       'subject-empty': [ 2, 'never' ],
       'subject-full-stop': [ 2, 'never', '.' ],