Docs improvement roadmap

[prrao87]

Async API Python docs

See #55: we need to think of good ways to show async Python examples that explain how to use it.

Add more TS examples

Many sections have only Python examples, but they could use TS examples that do the same thing.

Docs quality

• The structure of many pages is erratic (hard to follow) and the header have inconsistent naming
• Cleanup code snippets (remove tmp_db and other bloat that doesn't help the user)
• Many pages show only a partial subset of all the features the latest Python/TS APIs in the source code

Tasks

Improve docs on these pages first:

• Schema evolution @prrao87
• Vector and FTS index pages @prrao87
• Table updates @erik-wang-lancedb
• Versioning @erik-wang-lancedb
• Consistency @erik-wang-lancedb