This PR attempts to update the collectives introduction for the new teams API. Currently, this draft includes the following (but definitely needs review):
[x] Add intro text for team-based collectives
[ ] Add team-based API listing
[x] Deprecate active set-based API listing (see #40)
[x] Specify blocking/nonblocking semantics for collectives (see #44, openshmem-org/specification#228)
This PR attempts to update the collectives introduction for the new teams API. Currently, this draft includes the following (but definitely needs review):
Closes #46