Add guide how to handle ID-requests

[dalito]

@nmoust - You could try this out for the next ID-request. Is there something you would change now?

Closes #86

[nmoust]

@dalito I can try to make an ID range request (1 ID) from my personal email account and try to follow the steps the a maintainer should do. Maybe also take some screenshots while doing so.

[dalito]

Good idea to do a test as "another maintainer". A few screenshots could make it even clearer. For the command line I already provided the output. On the other hand, maybe the guide misses some instructions how to start working "on command line".

...or were you thinking of a alternative guide using only GitHub UI which would of course need more screenshots? Such guide could also be nice but may be very similar to the contributing screenshot set you already made.

[dalito]

ToDos before merge:

• add readme/index in new /docs dir
• link the new maintainer docs from main readme