docs: add CONTRIBUTING.md file

[qlrd]

What is this PR for?

CONTRIBUTING.md is a important file that guides new developers through the standards built by krux team through years. This isn't a monad and could be changed at time to time.

Changes made to:

• Code
• Tests
• Docs
• CHANGELOG

Did you build the code and tested on device?

• Yes, build and tested on

What is the purpose of this pull request?

• Bug fix
• New feature
• Docs update
• Other

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.31%. Comparing base (8c6579a) to head (8960644).

Additional details and impacted files

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  Coverage    97.31%   97.31%           
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  Files           83       83           
  Lines        10632    10632           
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  Hits         10346    10346           
  Misses         286      286           

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[odudex]

Needs a few changes

[qlrd]

@odudex, thought if is worth to down or maintain 3.12, wdyt?

[odudex]

IMO the source of this information is pyproject.toml. No need to replicate (and maintain) it elsewhere. You can add a link to the file mentioning user can learn about all python dependencies there.
No need to lower the requirement version. This is a decision the would require testing anyway.
Let project.toml speak for itself

[odudex]

Please ensure everything CONTRIBUTING.md states is true now. Code style, what is enforced by CI, what's not. It must be coherent with project's current status.
If new requirements and tools will later be adopted, then CONTRIBUTING can be adjusted accordingly.

[odudex]

1. Python version is stated three different ways across the repo, and CONTRIBUTING adds a fourth conflict.

• CONTRIBUTING.md:119 says minimum is 3.12.0 and "enforced by our CI".
• pyproject.toml:32 requires python = "^3.12.3".
• .github/workflows/tests.yml actually runs CI on 3.11 for every job (lint, pylint, tests, coverage).
• The claim "enforced by our CI" is therefore false. CI doesn't enforce 3.12 at all.

2. Markdown linting is not enforced.

• CONTRIBUTING.md:215 says rules "are enforced by CI, both for python and markdown code" and lists markdown rules at line 278.
• No markdown linter exists in .github/workflows/, and no .markdownlint*/.pymarkdown* config is present. There's an in-flight branch ci/pymarkdownlnt, but it hasn't landed.

3. Conventional-commit types list is incomplete.

• CONTRIBUTING.md:130-142 lists 8 types.
• .github/workflows/conventional-commits.yml allows feat,fix,docs,style,refactor,test,i18n,ci,chore,git.
• i18n and git are missing from the doc despite being CI-allowed.

4. Fork instructions are wrong.
   • CONTRIBUTING.md:67 shows git clone git@github.com:selfcustody/krux.git under "Fork Repository". That clones upstream, not a fork. There's no instruction to actually fork via GitHub or add the upstream remote.
5. CONTRIBUTING.md:260, 263 uses instanceof(...) — that's JavaScript. Python is isinstance(...). The "good example" wouldn't run.
6. CONTRIBUTING.md:226-231 Python skeleton is indented 3 / 6 / 12 spaces — black (which the project uses) will rewrite to 4-space. Example contradicts the formatter that CI runs.