Adding CONTRIBUTION.md

[rororowyourboat]

Context

MSML currently lacks a clear contribution guide. New contributors have to infer:

• How to set up the environment
• How to structure changes
• How to run tests or validate work

This increases friction and leads to inconsistent contributions.

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Goals

• Standardize the contribution workflow
• Reduce onboarding time for new contributors
• Make expectations explicit

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Scope

• Add CONTRIBUTING.md covering:

  • Environment setup
  • Repo structure overview
  • Coding and documentation expectations
  • How to submit PRs and run checks locally

• Link to dev container and package management docs where relevant

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Deliverables

• CONTRIBUTING.md at repo root
• References from README and docs

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Non-Goals

• Legal or governance policies
• Extensive style guides