Explore client-side validation for yard

The validation run will be heavy so it needs to be separated into a web worker.

It can share the reporting panels for regular code. The validation issues are reported in a text form, one line/paragraph of text for each issue. 

I would recommend each editor we currently work on has a shared Validation API and we reuse that.

The validator can work on the the directly YAML. YAML snapshot of the current state of the editor is passed for the validator once the validation is triggered. The validator will start and report the issues either as one bulk or incrementally while it finds them.