Add YAML schema as a source to the bashly JSON schema

[DannyBen]

An experiment to see if it is worth working with YAML as a basis for generating the bashly.json schema.

[DannyBen]

Tests are now passing, the schema seems to be valid now.
The only difference is that the custom-properties section is no longer called with $ref, and instead is plastered as is multiple times in the JSON file (in the YAML file, it is just once, using YAML anchors).

[DannyBen]

I squash-merged, and changed the template a little to be more readable.

[DannyBen]

@EmilyGraceSeville7cf - note that I moved the YAML source of the schema to the support folder.