Add support for websockets

[lucasdrufva]

Adds support for websockets.

HTTP dissector has been updated to support omitting the reason phrase as this is usually done when upgrading to websocket connection.

fixes #4578

[gpotter2]

Hi ! This looks pretty cool !

[codecov[bot]]

Codecov Report

:x: Patch coverage is 98.07692% with 3 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 78.74%. Comparing base (8e08cbf) to head (60a13b7). :warning: Report is 176 commits behind head on master.

Files with missing lines	Patch %	Lines
scapy/contrib/websocket.py	97.97%	3 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4579      +/-   ##
==========================================
- Coverage   81.62%   78.74%   -2.89%     
==========================================
  Files         358      334      -24     
  Lines       85652    80602    -5050     
==========================================
- Hits        69915    63470    -6445     
- Misses      15737    17132    +1395     

Files with missing lines	Coverage Δ
scapy/layers/http.py	80.54% <100.00%> (-1.90%)	:arrow_down:
scapy/contrib/websocket.py	97.97% <97.97%> (ø)

... and 284 files with indirect coverage changes

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