Create a file with tag name / commit sha in the generated UF2 firmware

[urish]

This way, people can easily tell which version they have on their demo board. Inside the GitHub action, you can get the tag name from ${{ github.ref_name }}

[psychogenic]

Augmented workflow to:

1. touch a file with the release tag in the name, so you can just:

   os.listdir() ['config.ini', ... 'release_v0.9.11c', 'shuttle_index.json', ...]

2. create UF2 files with actual versions, like tt-demo-rp2040-v0.9.11c.uf2