Implement silent comment command

[dspinellis]

Implement missing POSIX feature regarding scripts starting with #n.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 0.00%. Comparing base (56ad3e9) to head (8ff9dd1).
⚠️ Report is 16 commits behind head on main.

Files with missing lines	Patch %	Lines
src/uu/sed/src/compiler.rs	0.00%	12 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #120   +/-   ##
=====================================
  Coverage   0.00%   0.00%           
=====================================
  Files         13      13           
  Lines       2720    2732   +12     
  Branches     234     240    +6     
=====================================
- Misses      2720    2732   +12     

Flag	Coverage Δ
macos_latest	0.00% <0.00%> (?)
ubuntu_latest	0.00% <0.00%> (ø)
windows_latest	0.00% <0.00%> (ø)

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[cakebaker]

Thanks!