feat: Create subcommand `docs` that will generate list of images from all recipes

[gmpinder]

Inspired by an idea from this podcast. We should include a way to recursively search through the project for all recipes and create a list of the images that can then be added to a doc. This is similar to how terraform-docs would work.

First pass I think would be to print it in markdown so that it's easy to add to a README.md.

[fiftydinar]

I think that bluebuild-docs would be beneficial to generate offline documentation from https://blue-build.org/ too

Or maybe this function is better for BlueBuild Workshop