Create CONTRIBUTING.md

[emnul]

The CONTRIBUTING.md file should:

• Provide contribution guidelines for contributors such as
  • How to submit a pull request
  • How to report a bug (providing a bug report template would be ideal)
  • How to request an "enhancement"
  • Style Guide / Code conventions
  • Code of conduct
• Provide links to important resources
  • Comms channels where devs can ask for help
  • Link to docs
  • Issue tracker / bug report tool
• Provide testing guidelines