Show rule explanation popup on hover in `pyproject.toml`

I noticed that when I hover my cursor over a `# noqa: ABC123` comment in a `.py` file, it shows a popup explaining what the `ABC123` rule is.

My suggestion is to have this popup also on the `pyproject.toml` file, when you hover over rules in the `tool.ruff.[select|ignore|unfixable]` sections, for example.

Start by tracing the existing hover handling for `# noqa: ABC123` comments in Python files, then inspect how language features are registered for `pyproject.toml`. The change is complete when hovering rules in the `tool.ruff.select`, `ignore`, and `unfixable` sections displays the corresponding rule explanation.

Written by the indexing model from the issue text.