cli: Use clap-mangen to generate man pages

[felinira]

We can't merge this as of now, this renders subcommands as separate man pages, which for us would be way too noisy and unnecessary.

See: clap-rs/clap#5337

SUBCOMMANDS
       wormhole-rs-send(1)
              Send a file or a folder

Maybe we need to do something differently here.

Closes #231

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 37.90%. Comparing base (bc997d8) to head (fee1608).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #233      +/-   ##
==========================================
- Coverage   38.03%   37.90%   -0.13%     
==========================================
  Files          18       18              
  Lines        3163     3163              
==========================================
- Hits         1203     1199       -4     
- Misses       1960     1964       +4     

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