This CL adds parsing of the `workgroup_size` function decoration.
Change-Id: Ia90efc2c014ac0e1614429280cc903d30cf8171d
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/28663
Commit-Queue: dan sinclair <dsinclair@chromium.org>
Reviewed-by: Sarah Mashayekhi <sarahmashay@google.com>