delta-docs: Automate publishing docs site

[jakebellacera]

Automate publishing of docs site using Github Actions so that anyone can update the docs site without needing help from maintainers.

Acceptance criteria

• Docs site is published via Github Actions.
• Specific versions of API docs are built during deployment (e.g. 4.0.0)
• Whenever a change to /docs folder is merged in delta-io/delta, publish the docs.
• Whenever a new release is published, publish the docs.
• Support manual deployments for debugging purposes.