We didn't have a grammar defined for metadata sections in the past, and

while we've loosely modeled our metadata structure off of YAML and

Git's metadata format, neither option was really sufficient.
We'll be introducing a grammar for metadata. That's not here in this

change, but in preparation, all sample metadata in the spec has been

updated for the planned grammar. The section on the metadata language

and the reserved future format option for the metadata sections has

been updated accordingly.

Built the docs. Checked the relevant sections to make sure they were

using the right syntax.