docs(ci): new docs to explain plugins and cpan libs CI

[sdepassio]

Description

New developer documentations to explain plugins CI and cpan libraries CI.

Fixes CTOR-1383

Type of change

• Patch fixing an issue (non-breaking change)
• New functionality (non-breaking change)
• Functionality enhancement or optimization (non-breaking change)
• Breaking change (patch or feature) that might cause side effects breaking part of the Software

Checklist

• I have followed the coding style guidelines provided by Centreon
• I have commented my code, especially hard-to-understand areas of the PR.
• I have rebased my development branch on the base branch (develop).
• In case of a new plugin, I have created the new packaging directory accordingly.
• I have implemented automated tests related to my commits.
  • Data used for automated tests are anonymized.
• I have reviewed all the help messages in all the .pm files I have modified.
  • All sentences begin with a capital letter.
  • All sentences end with a period.
  • I am able to understand all the help messages, if not, exchange with the PO or TW to rewrite them.
• After having created the PR, I will make sure that all the tests provided in this PR have run and passed.

[Evan-Adam]

I'm ok with the doc, I tryied to rebase before merging, the CI failed because of network latency, we need to restart it