Can test here https://www.jsonschemavalidator.net/
Copy whole schema from the PR, and use your json for assets.
Or this one:

{
  "name": "test",
  "version": "11",
  "description": "description",  
  "assets": [
    {
      "name": "a",
      "type": "script",
      "importmap": true,
      "importmapName": "aaa",
      "importmapScope": "bbb"
    }
  ]	
}

the content .gitignore should be part of your global .gitignore file not of this repo

It a default gitignore we should have in all repos,
Why this repo should have an exception?

the content you commit was something that should be in the global ignore file for each person using git but yep true I thought joomla did it the right way but isn't ;-)

thanks