[UTILS] Improve b2view TUI

The b2view command-line TUI (installed as a project script) allows to browse visually inspect a .b2nd or .b2z/.b2d file/dir. It has different views (tree, meta, vlmeta, data), but more love is needed to make it working in a smoother way and/or adding new features.

Also, b2view is not mentioned anywhere in doc/. Users who install python-blosc2 and want to visually inspect a .b2nd or .b2z file have no way to discover it from the docs.

Suggested work:
- Use real-world datasets (e.g. coming from parquet files in Hugging Face), and assess navegability on them. Try to improve visual aspects and browsability in general.
- Add a short section to doc/getting_started/overview.rst (or a new tools.rst) describing b2view, what file types it supports, and how to launch it
- Add a screenshot or short ASCII rendering of the TUI output
- Link it from the parquet-to-blosc2 docs (issue 3 above) since that tool and b2view are often used together