Use tabs in documentation to show different ways to set configuration

[tomwhite]

For example, on this page for setting an executor, there could be documentation tabs for doing the same thing using Spec, config, yaml, and env vars.

Suggested by @norlandrhagen, and inspired by https://virtualizarr.readthedocs.io/en/stable/usage.html.

[TomNicholas]

Great idea! There could also be different tabs for examples using different executors.