Document `.2EX` analysis files

[Holzhaus]

Similar to .EXT files which added new tag types, the .2EX files seem to contain some new tags:

Tag	len_header	len_tag for demo track
PWV7	24	77622
PWV6	20	3620
PWVC	14	20

Judging from the tag names and sizes, these seem to be related to waveforms.

[brunchboy]

If you could analyze and document these, it would be most appreciated! Let me know if you have any trouble figuring out how my diagram generator works. The analysis files are actually documented in the Crate Digger project, which is what parses them, let me see if I can move this issue.