MAINTAINERS: add "RUST [RUST-ANALYZER]" entry

MAINTAINERS: add "RUST [RUST-ANALYZER]" entry

This entry will handle the support for `rust-analyzer`, which at the
moment is essentially about the `scripts/generate_rust_analyzer.py`
script.

It is one more subentry of the Rust subsystem. The new branch is
already part of linux-next and will be used to send PRs to be merged
into rust-next.

Tamir and Jesung will take care of it. They have both been active around
the `rust-analyzer` support for a while.

Acked-by: Tamir Duberstein <tamird@kernel.org>
Acked-by: Jesung Yang <y.j3ms.n@gmail.com>
Acked-by: Andreas Hindborg <a.hindborg@kernel.org>
Link: https://patch.msgid.link/20260115214545.63262-1-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>