[Mastodon] Add support for favo(u)rites

[daniels1989]

There's already support for bookmarked posts, but apparently there's also favo(u)rites. Api endpoint returns the same data as the bookmarks endpoint, so I guess it's just a matter of adding

def account_favourites(self):
    endpoint = "/v1/favourites"
    return self._pagination(endpoint, None)

on line 210, and

class MastodonFavouritesExtractor(MastodonExtractor):
    """Extractor for mastodon favourites"""
    subcategory = "favourites"
    pattern = BASE_PATTERN + r"/favourites"
    example = "https://mastodon.social/favourites"

    def statuses(self):
        return MastodonAPI(self).account_favourites()

on line 137?