show sniff codes in the docs

[przemekhernik]

No description provided.

[jrfnl]

As per the CONTRIBUTING guide:

Requesting/Submitting New Features

Ideally, start by opening an issue to check whether
the feature is something which is suitable to be included in PHP_CodeSniffer.

It's possible that a feature may be rejected at an early stage, and it's better to find out before you write the code.

It is also good to discuss potential different implementation options ahead of time and get guidance for the preferred option
from the maintainers.

And:

Submitting your pull request

Some guidelines for submitting pull requests (PRs) and improving the chance that your PR will be merged:
...

• Only open your PR when you've finished work on it, and you are confident that it is ready for review.

I suggest you open an issue to discuss this and close this PR.

[przemekhernik]

I'll make you more work than without my engagement here, sorry for this 😅 I'll do this properly as you said :)