Add comments to requirements.txt

[lucacome]

Adds comments on how the file was generated, how to update it if introducing a new dependency and why the dependency is required.

[codecov-commenter]

Codecov Report

Merging #3382 (86dad51) into main (09364eb) will increase coverage by 0.00%.
The diff coverage is n/a.

❗ Current head 86dad51 differs from pull request most recent head a0dcb0d. Consider uploading reports for the commit a0dcb0d to get more accurate results

@@           Coverage Diff           @@
##             main    #3382   +/-   ##
=======================================
  Coverage   51.56%   51.56%           
=======================================
  Files          60       60           
  Lines       16675    16678    +3     
=======================================
+ Hits         8598     8600    +2     
- Misses       7785     7788    +3     
+ Partials      292      290    -2     

Impacted Files	Coverage Δ
...ternal/k8s/appprotect/app_protect_configuration.go	86.16% <0.00%> (-0.58%)	⬇️
cmd/nginx-ingress/flags.go	29.85% <0.00%> (-0.44%)	⬇️
internal/k8s/configuration.go	95.76% <0.00%> (+0.36%)	⬆️

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