Add a team charter for rustdoc team

[nikomatsakis]

Metadata
Point of contact	@GuillaumeGomez
Team(s)	rustdoc
Goal document	2025h2/rustdoc-team-charter

Summary

Over the next six months, we will do the following:

• Write the team charter in the rust-forge

Tasks and status

• Org decision (rustdoc )

[nikomatsakis]

This issue is intended for status updates only.

For general questions or comments, please contact the owner(s) directly.

[GuillaumeGomez]

Done in rust-lang/rust-forge#852.