Declare `name` and `creation_panel` in the `calendar_provider` schema

[jobisoft]

schema/calendar-provider.json declares only capabilities, but
parent/ext-calendar-provider.js also reads name (line 114, and 645 for the
New Calendar type list) and creation_panel (596, 646).

They work, additionalProperties: UnrecognizedProperty passes them through,
so this is only about discoverability and schema checking.

"name": {
  "type": "string",
  "optional": true,
  "preprocess": "localize"
},
"creation_panel": {
  "type": "string",
  "optional": true,
  "format": "relativeUrl",
  "preprocess": "localize"
}

Putting this here as a reminder when implementing it as an API.