feat(use_filenaming_convention): add support for $ prefix

[brandonmcconnell]

Summary

Adds support for dollar-sign-prefixed filenames, a convention used by TanStack Start: https://tanstack.com/start/latest/docs/framework/react/guide/routing

Relates to biomejs/biome#8007

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[brandonmcconnell]

@ematipico I see you closed this PR. Did I do something incorrectly here?

[ematipico]

As written at the top of the file, it's code generated. Once the code is merged, the docs will be automatically updated

[brandonmcconnell]

@ematipico Good call, thanks. I misunderstood these instructions from https://github.com/biomejs/biome/blob/main/CONTRIBUTING.md#documentation

If your PR involves new features, or changes to existing features, documentation must be updated as well. For rules, assists, and their options, this is done using inline rustdoc documentation.

When other documentation updates are required, such as new formatter options, a PR should be created against the next branch of our website. When doing so, please link the documentation PR from the PR that introduces the feature.

[ematipico]

Feel free to send a PR to improve it, if you think it's not clear enough