Add "description"s guidelines for Permissions API descriptions

[bershanskiy]

Descriptions that are not linted are susceptible to copy-paste errors, as can be seen in #5909. I propose we:

• document already existing practice in Data guidelines by adding:

  Permissions API permissions (api.Permissions.*_permission.__compat.description)

  Document Permissions API permission called [permissionname] as api.Permissions.[permissionname]_permission and add a description that reads "<code>[permissionname]</code> permission"
  For example, the Geolocation permission is named geolocation_permission with the description text <code>geolocation</code> permission, like this:

  {
   "api": {
     "Permissions": {
       "__compat": {},
       "geolocation_permission": {
         "__compat": {
           "description": "<code>geolocation</code> permission",
           "support": {}
         }
       }
     }
   }
  }
  

• create a linter to fix errors like those in Fix api.Permissions.*.__compat.description #5909

CC @vinyldarkscratch