Guidance docs for contributing to GitHub

[harisood]

Summary of issue

We need to create documentation on how to contribute to the repo and to GitHub, including:

• Walkthrough of how to contribute to the specification
• Walkthrough for SATRE team members on how to contribute to the project team issue board

What needs to be done?

• Create walkthrough for contributing to the specification repo
• Create walkthrough for SATRE team members to track issues on the issue board
• Test these processes with SATRE team members
• Iterate and review

Who can help?

• @arronlacey for drafting
• KO, JB & AC for testing

Issue checklist

• I have assigned the appropriate work package label to this issue, and added any other relevant labels
• I have added this to the SATRE backlog (public) project board
• I have assigned this issue to at least one person on the SATRE team

[harisood]

Once these are created we'll run through them with project team members to see if they are fit for purpose!