Improve skool2asm.py's handling of standard input
Improve skool2html.py's handling of a skool file on standard input
Rewrite the revision histories in reverse chronological order
Remove the 'z' from EntryTypes in the [MemoryMap:UnusedMap] section
Update the documentation on image masks
Update the Features section of the 'What is SkoolKit?' page and setup.py
Update the documentation on extension modules