OSD type file dilemma

[tihuan]

Context:

1. OSD types file is for v3, which is misleading with v4 library sometimes -_-
2. Brain storm: Should we use GPT to generate type file?
3. Seems not a huge problem for our limited customization of OSD.. maybe kick the can for now but add a HUGE caveat, so people are aware of the type mismatch

DoD:

1. Find out if there's an open issue for v4 types and link it to our code as comment
2. Add code comment warning that type file is in v3, so people are aware that TS could throw false errors

[tihuan]

Decrease to p2, since I don't think we'll touch openseadragon frequently enough that the misleading type issue will have large enough impact