Team assignment: Add contributing guidelines

[jackxujh]

User story Add contributing guidelines for the repository.

Acceptance criteria

• It includes following sections:
  • What to do before started
  • How to report bugs, enhancements
  • How to make pull requests
  • Code styles and conventions
• Refer to kb article and examples linked here
• First draft available to review before Monday morning.
• Each team member review the draft, and each member provides at least one point to improve in the draft.
• The guideline is reviewed and approved in the team.

Definition of Done We have a CONTRIBUTING.md at master branch.