Add changelog generation, releases, publish pypi package

[nongrata081]

🚀 The feature, motivation and pitch

• Would be nice to have automatically generated changelog from commit history. Maybe github's generated release notes or with git-cliff (example). Then it's easier to reason about what changes were introduced when.
• Would also be nice to see torchchat/releases populated as new updates are rolled out (e.g. like in torchtune/releases). Then it's easier to switch between different versions to test & reproduce functionality.
• Would also be nice to have a possibility to install torchchat via pip install as a pypi package. The currently existing torchcat pypi package doesn't represent the latest contents of this repo. Then it's easier to install torchchat with just one cli command, as with torchtune pip install torchtune

Alternatives

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Additional context

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RFC (Optional)

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