Add manifest property "data_collection_permissions"

[aecreations]

The new data_collection_permissions key in the extension manifest will soon be required. See https://mzl.la/blog-data-consent-firefox-nightly.

The following should be added to the extension manifest:

"browser_specific_settings": {
    "gecko": {
      // ...
      "data_collection_permissions": {
        "required": [
          // TBA
        ]
      }
    }
  }