Add a contribution guidelines to the root of the repo

[ori-shalom]

Suggestion to add a contribution.md file to the root of the repo. This file can be referenced from the README.md file with a link.

I expect this file to explain how one might contribute to this project.

• How to open an issue and what to include in each issue type (bug, feat, etc.).
  • How to format the title
• How to build and test the project (pretty trivial from what I saw)
• How to issue a PR + requirements for PR
  • How to name the branch
  • Verify all tests pass and all CI checks pass
  • Make sure to go fmt and use gosimports?
  • Add tests for whatever change you make
  • Make sure to rebase/merge your branch to include the latest changes
  • Add/update documentation if needed
  • Add a line to changelog?
  • keep PR short and concise if PR is touching multiple different topics consider splitting to different PR
  • should PR must reference an issue?