Integrate autobahn tests

[nhooyr]

Closes #7

Will not keep these though as they are janky to integrate in CI,
not documented well and very slow. They were extremely useful for
making sure my implementation works right now but I'd rather have my own Go tests.

[codecov]

Codecov Report

Merging #43 into master will increase coverage by 14.82%.
The diff coverage is 73.42%.

@@             Coverage Diff             @@
##           master      #43       +/-   ##
===========================================
+ Coverage   51.89%   66.71%   +14.82%     
===========================================
  Files          11       11               
  Lines         555      634       +79     
===========================================
+ Hits          288      423      +135     
+ Misses        230      177       -53     
+ Partials       37       34        -3

Impacted Files	Coverage Δ
opcode.go	100% <ø> (ø)	⬆️
opcode_string.go	0% <0%> (ø)	⬆️
statuscode.go	68% <100%> (+41.68%)	⬆️
statuscode_string.go	25.92% <15.38%> (+25.92%)	⬆️
websocket.go	78.18% <78.68%> (+20.85%)	⬆️
header.go	91.66% <0%> (+16.66%)	⬆️

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