They're in a new location over on John P.'s website
(should we purhapse integrate them into Tux Paint proper?)
(h/t sechidis & whoever on #tux4kids IRC channel who helped them)
Documenting Mark Kim's recent changes:
* Less CPU-hungry progress bar (during Stamp loading)
* Verbose debugging options
* (Also, mentioned debugging _at all_, in INSTALL.txt)
Bumping version to 0.9.23a, to match the test build he's working
on for macOS.
Documenting a few recent changes & contributors.
Also, move AUTHORS out of docs/en/ and back into docs/ top-level dir
(since it's unlikely to get translated & maintained!)