Generate RULES.md in human/ai-readable format

[slaFFik]

Description

Fixes #78.

I used this prompt to generate it.

go through reach rule in sniff files and create an AI-readable RULES.md file that I can then reference in all my other projects. I want ai
to read the file and understand how exactly WPForms PHPCS rules differ (modify, extend, or add new rules) from default WordPress PHPCS rules. The
idea is that in every new project I can reference this file, and AI, when writing code, will be able to understand that (for example) there should
 be a new line between `case` statements, or a new line before `return` statement, or a new line after the function declaration inside the
function body, and so on. Ask clarification questions if something is unclear.

---

User answered Claude's questions:
  ⎿ Should RULES.md focus on actionable coding guidelines ("do this, not that") or also include technical implementation details about how sniffs work? → 
    ⎿  Actionable guidelines only

  ⎿ Should the document include examples of correct/incorrect code for each rule?
    ⎿ Yes, show code examples
    
  ⎿ How should rules be organized in the document?
    ⎿ By category (Comments, Formatting, PHP, etc.)

  ⎿ Should the document explain which WordPress PHPCS rules are disabled/modified, or only focus on new/additional rules?
    ⎿ Include disabled WPCS rules, Include modified WPCS rules

After that, I asked claude to review and expand on the rules and the .md file. You can see the results in the 2nd commit.

I haven't included CLAUDE.md file as I think it doesn't matter for this usecase.

If merging, the branch should be squashed-n-merged (so a single commit lands into the main branch).

[kagg-design]

Thank you, @slaFFik, great addition!

I will use it in our projects.