Add v2.3 release notes

Add release notes for v2.2

Fix minor formatting errors

Version 2.0 of the PGD Community SDL2 Headers

Remarks:
- This version differs only a little bit from the original headers by
Tim Blume aka END (see https://github.com/ev1313/Pascal-SDL-2-Headers).
- This version is kind of a fallback-version if introduction of typed
integers (which will be started with the merge of PR #4) turns out to be
an (unexpected) failure.