Improvements
- Add `CauseGroup.__eq__`.
- Add `CauseGroup.__new__`.
- Add `FormData.__eq__`.
- No `content length` / `tarnsfer encoding` headers are sent when we are not sending anything.
Having these headers caused Discord's websocket to never read want we send to it (since yesterday night).
Bug fixes
- `WebSocketCommonProtocol.close_connection` did not handle `GeneratorExit` correctly.
Renames, Deprecation & Removals
- Rename `FormData` to `Formdata`. Old version is still a valid import for now.
- Deprecate `filename` parameter of `FormData.add_field` in favor of `file_name`.