Suggestion: add advice about code development whilst a job is running on the server

[remlapmot]

You have helpful advice on the Code reviews and git workflow pages but I feel on either the Job server page or at the bottom of the Getting Started guide it would be helpful to include some advice about developing additional code once you have set a job running on the server and you're waiting for it to finish and hence waiting for the outputs to be released.

I assume that the advice would be to develop the new code on a new branch (because then you can obtain code review on a resulting PR). And I would assume it's preferable to wait before merging this new branch into master/main until the outputs from the job have first been merged (although perhaps this merge order isn't critical if it wouldn't create any merge conflicts or if you're leaving the outputs on the released-candidates branch).