Expose `automerge::AutoCommit::with_actor()` through `AMcreate()`.
Add notes to clarify the purpose of `AMfreeStack()`, `AMpop()`,
`AMpush()`, `AMpushCallback()`, and `AMresultStack`.
source files.
Normalize the header include statement within the documentation.
Limit `AMpush()` usage within the quickstart example to variable
assignment.
Rename `AMdup()` to `AMclone()` to match the WASM API.
Rename `AMgetActor()` to `AMgetActorId()` to match the WASM API.
Rename `AMsetActor()` to `AMsetActorId()` to match the WASM API.
