[dep] Update websocket-client and attrs to major releases

Changes

• websocket-client contains mostly Py2 drop:
  • https://github.com/websocket-client/websocket-client/blob/master/ChangeLog
• attrs contains Backward-incompatible Changes which doesn’t seem to concern DuniterPy:
  • https://github.com/python-attrs/attrs/blob/main/CHANGELOG.rst
• categorize deps: network, parsing, crypto
• CI: Define extends on a one-liner

websocket-client project revival

That's a good news, a new contributor took over the maintenance on websocket-client project. I felt the project unmaintained when we decided to go with it. It seems it's really moving forward:

• https://github.com/websocket-client/websocket-client/issues/684