feat: json schema

[EmilyGraceSeville7cf]

There are several possible ways of utilizing this schema (YAML extension is required in VS Code to make them work):

• It can be referenced directly # yaml-language-server: $schema={{schema url in this repository}} in ~/.tran/tran.yml, this is a manual approach because requires user to put a full URL by hand.
• It can be put in SchemaStore and referenced there like this. This approach ensures that whenever user edits ~/.tran/tran.yml they get the latest hints for it.

If this PR is accepted this schema is referenced in SchemaStore to automatically enable validation for ~/.tran/tran.yml.