Enable json validation for sdk

Luci builder configs have now been available in separate repos. This CL enables validation of the config json file format for flutter recipes.

Change-Id: Ice879fe16cf47771c8ebb9450c1882154ebc9753
Reviewed-on: https://flutter-review.googlesource.com/c/recipes/+/5340
Commit-Queue: Keyong Han <keyonghan@google.com>
Reviewed-by: Tong Wu <wutong@google.com>
25 files changed
tree: 0d19cdb67086d49804baa895768f45572e1aa642
  1. infra/
  2. recipe_modules/
  3. recipes/
  4. .gitignore
  5. .style.yapf
  6. OWNERS
  7. recipes.py