Mux migration

[morgante]

We need a migration for the Mux SDK, similar to this OpenAI migration. Specifically, we need to convert repos from using this SDK to using this SDK.

Process

1. Start by gathering a set of before/samples in the markdown file. You can use this repo as a sample to gather things from.
2. Use grit patterns test --filter=your_pattern_name to test that the pattern transforms before/after correctly.
3. Iterate (usually in the studio) until all cases are covered).

Acceptance criteria

1. The pattern must be sufficiently general - it should not cover only a single example.
2. You must include at least 5 test cases in the markdown file.
3. The pattern should fully cover converting this sample repo to the new SDK