Rework cookbook

[digitaldogsbody]

• Reformats the existing cookbook examples per @giacomomarchioro's suggestion to use a table for the recipe+json links
• Adds a brief introduction to the cookbook docs
• Adds the awesome-pages plugin and uses it to autogenerate the navigation for the cookbook recipes
• Moves existing cookbook recipe python to separate files and updates recipes
• Enables pymdownx.snippets to load compile python code into the markdown
• Adds a script in utils/ that checks the validity of the cookbook recipes
• Adds a new workflow that calls the script
• Adds recipe doc + code for 0017-transcription-av
• Adds recipe doc + code for 0230-navdate
• Updates the AutoFields helper to allow the AutoLabel magic to work on other classes that have .label properties (Allow AutoLabel to work in other places that have a .label property #155)
• Includes the changes from Fix serialization errors with datetime etc #151 and Fix skeleton modifier bug + add ManifestRef changes #154 due to basing/branching fun. They should be merged first, and if either is changed before merge, there might be conflicts.

Closes #155

[digitaldogsbody]

Once this is merged, the instructions in #129 will need to be updated a bit and the cookbook_skeletons branch updated to pre-enter the likely snippet names for convenience

[giacomomarchioro]

It looks great! Immense work. I'm just curious, why not consider test_cookbook an integration test and run it using unittest?