Add sheet

[Pante]

Describe the changes
This PR adds modal & persistent sheets. It resolves #42.

Checklist

• I have read the CONTRIBUTING.md.
• I have included the relevant unit/golden tests.
• I have included the relevant samples.
• I have updated the documentation accordingly.
• I have updated the CHANGELOG.md if necessary.

[auto-maid]

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You're seeing this because the docs/samples were updated.

[kawaijoe]

While not a bug with the sheet per se, I think it could be nice if we only allowed one sheet to show at a time.

Screen.Recording.2024-12-06.at.10.02.33.PM.mp4