This patch implements the `FontFace` interface, but with some caveats
1. The interface is only exposed on `Window`. Support for Workers will
be handled in the future.
2. The concept of `css-connected` `FontFace` is not implemented, so
`@font-face` rules in stylesheets will not be represented in the DOM.
3. The constructor only supports using `url()` strings as source
and `ArrayBuffer` and `ArrayBufferView` are not supported yet.
A skeleton implementation of the `load` method of `FontFaceSet` is also
implemented in this patch. The intention is to support some web pages
that don't load without this method.
Signed-off-by: Mukilan Thiyagarajan <mukilan@igalia.com>
