docs: add contribution guide and update readme

[pythonpete32]

Description

• add Contribution Guidelines
• update Readme

Task: DX-59

[heueristik]

This contribution guide assumes that there are issues for certain tasks being labeled properly that contributors can take over. However, our task planning and creation is generally done in JIRA.

Is the plan to move away from JIRA for the dev portal and use GH issues?

[pythonpete32]

This contribution guide assumes that there are issues for certain tasks being labeled properly that contributors can take over. However, our task planning and creation is generally done in JIRA.

Is the plan to move away from JIRA for the dev portal and use GH issues?

no but the task requested to add contribution guidelines. I believe the goal is more to allow external people to fix small bugs or maybe to add tutorials (i know we dont have a tutorials section yet). JIRA will still be the tool we use internally. AFAIK our JIRA is private

[heueristik]

I don't see how this will lead to satisfying contributions if the tasks backlog is not visible to external collaborators and does not have "good first issue" labels.

Maybe an automated syncing between JIRA and developer portal related tasks is the answer. This is a general problem I see with all our repos: They are not really open/friendly to external collaborators because our backlog is not visible.

The PR itself LGTM so I'll approve this PR.