docs: add README on semantic commit messages (!3)

Co-authored-by: Constantin Simonis <constantin@simonis.lol>
Reviewed-on: https://git.simonis.lol/projects/casino/pulls/3
Reviewed-by: Constantin Simonis <constantin@simonis.lol>
Co-authored-by: Jan-Marlon Leibl <jleibl@proton.me>
Co-committed-by: Jan-Marlon Leibl <jleibl@proton.me>

README.md

@@ -0,0 +1,34 @@
+# How to: Semantic Commit Messages
+
+See how a minor change to your commit message style can make you a better programmer.
+
+Format: `<type>(<scope>): <subject>`
+
+`<scope>` is optional
+
+## Example
+
+```
+feat: add hat wobble
+^--^  ^------------^
+|     |
+|     +-> Summary in present tense.
+|
++-------> Type: chore, docs, feat, fix, refactor, style, or test.
+```
+
+More Examples:
+
+- `feat`: (new feature for the user, not a new feature for build script)
+- `fix`: (bug fix for the user, not a fix to a build script)
+- `docs`: (changes to the documentation)
+- `style`: (formatting, missing semi colons, etc; no production code change)
+- `refactor`: (refactoring production code, eg. renaming a variable)
+- `test`: (adding missing tests, refactoring tests; no production code change)
+- `chore`: (updating grunt tasks etc; no production code change)
+
+References:
+
+- https://www.conventionalcommits.org/
+- https://seesparkbox.com/foundry/semantic_commit_messages
+- http://karma-runner.github.io/1.0/dev/git-commit-msg.html