Derive Hash for the QoS enum

[svanharmelen]

We would like to be able to use the QoS as part of a HashMap key (e.g. HashMap<((String, QoS), ...>), but for that QoS needs to implement the Hash trait.

[fafhrd91]

thank!

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 71.04%. Comparing base (e8e496d) to head (62b0fca).
Report is 1 commits behind head on master.

Files	Patch %	Lines
src/types.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #175      +/-   ##
==========================================
- Coverage   71.09%   71.04%   -0.06%     
==========================================
  Files          52       52              
  Lines        8709     8717       +8     
==========================================
+ Hits         6192     6193       +1     
- Misses       2517     2524       +7     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[svanharmelen]

Thanks for the super quick merge and release @fafhrd91 ❤️