Documentation updates for 1.2 for WinML (#3149)

* api goverannce draft

* Update CONTRIBUTING.md

updated for ABI proposals

* Update CONTRIBUTING.md

* Update CONTRIBUTING.md

* Incomplete, a draft iteartion of 2 more changes - api docs and high levle design

* pushing to see how the picture size works on screen.

* added 2 charts on api choice and distribution choice

* details on contract checking

* lint cleanup and links

* PR feedback.

* fixed markdown and lists

* more markdown and lists

* fixed broken links

* PR feedback

* commas

* PR comments from nick

* PR feedback

* fixed build section

Co-authored-by: Nick Geisler <36938193+ngeisler11@users.noreply.github.com>