egg: ws-client 0.2.1

[Ka-tsùn Lo̍h]

Hi all,

This is a minor update to the WebSocket client extension that was
submitted a week ago:

- replaced some foreign invocations with scheme code where the
functionality has already been implemented by another egg.
- updated meta files and documentation, including fixing some
discrepancies in the .egg file.
- added a tests/ folder, containing a single, very ad-hoc sanity check.

with thanks to very helpful feedback from Vasilij Schneidermann.

The URI for the release-info file has not changed from 0.2.0, but
since it hasn't yet been added to `egg-locations`, here it is again:
https://raw.githubusercontent.com/lohkatsun/ws-client-egg/main/ws-client.release-info

Thanks!

Ka-tsùn