[WIP] Expand information about project policies in Contributing Guide

[StackScribe]

Summary

We need to better define Keptn project policies in the "Contributing Guide".

Some inspiration may be found by looking at the Kubernetes documentation such as https://github.com/kubernetes/community/blob/master/contributors/guide/pull-requests.md#why-was-my-pull-request-closed .

Please add items to this ticket as comments. We will review when we refine this ticket.

Specific points

• In general, you should work on one issue at a time.
• When you are assigned a ticket, we expect to see an PR or other activities within a few days and no more than a week.
• If you are assigned a ticket then find you can not work on it immediately, please communicate this to the team so that the ticket can be reassigned. If you do this and have completed some work that is useful to whoever takes over the ticket, your name will be associated with the ticket when completed. If you just disappear, we will take the ticket back after two weeks of inactivity and you may not be credited with the work you did.
• The same policy applies after you submit a PR. You should respond to all comments within a few days. Tickets with no activity after two weeks will be reassigned. If you communicate with the team that you can not complete the ticket and your work is used, your name will be associated with the ticket. If you just disappear, you may not be credited with the work you did.

[mowies]

This ticket will be merged with #3095

[mowies]

closed in favor of #3095