Move long messagequeue comment to doc.go

[gammazero]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 60.42%. Comparing base (699c35b) to head (4531089).
Report is 1 commits behind head on main.

@@            Coverage Diff             @@
##             main     #814      +/-   ##
==========================================
- Coverage   60.48%   60.42%   -0.07%     
==========================================
  Files         244      244              
  Lines       31101    31101              
==========================================
- Hits        18812    18792      -20     
- Misses      10610    10629      +19     
- Partials     1679     1680       +1     

Files with missing lines	Coverage Δ
...tswap/client/internal/messagequeue/messagequeue.go	84.15% <ø> (ø)

... and 9 files with indirect coverage changes