Document workstreams (under a different name)

[joshuagl]

Document workstreams and how to sign up. Migrate relevant portions of https://docs.google.com/document/d/1L1gEJMBIvE0IbpFi23FOUByDYlItSYPPJmKdhvJQYsg/ to this repo.

[MarkLodato]

Also document on slsa.dev/community

[joshuagl]

Arnaud pointed out that the term "workstream" is already in use at OpenSSF to describe work under the 10 streams of investment that were identified following the Open Source Security Summit II in Washington.

Let's find another term as part of the documentation effort.

Ideas:

• taskforce
• taskgroup
• committee
• team

[joshuagl]

Brian B has proposed Special Interest Group (SIG)