https://git.beagleboard.org/docs/docs.beagleboard.io/-/merge_requests/79#note_15599

- Remove slack link
- Add link to beagleboard forum

Signed-off-by: Ayush Singh <ayushdevel1325@gmail.com>

- Remove slack link
- Add link to beagleboard forum

Signed-off-by: Ayush Singh <ayushdevel1325@gmail.com>

- Specify language for codeblocks to fix build warnings

Signed-off-by: Ayush Singh <ayushdevel1325@gmail.com>

- Also change venv name to .venv since zsh scripts to auto load venv
  assume this path by default

Signed-off-by: Ayush Singh <ayushdevel1325@gmail.com>

Fix some code, code-block, and literalinclude warnings

- Allows simplifying local setup instructions without docker.
- Also use python venv (which is builtin with standard python3).
- Install as much stuff to python venv as possible to make things more
  cross-plaform.
- Fix some minor bash snippets which were not labled (and thus were
  being treated as cpp snippets)

Signed-off-by: Ayush Singh <ayushdevel1325@gmail.com>

- Add instructions to used docker (or podman) for building and testing
  docs locally.

Signed-off-by: Ayush Singh <ayushdevel1325@gmail.com>