Add intro paragraph

[rkratky]

A short explanation of the purpose of these guidelines needs to be added to prevent misunderstandings. See #7 (comment)

[CBID2]

Hi @rkratky! :) I'd like to work on this issue.

[bergerhoffer]

Hi @CBID2. This project doesn't have much of a team maintaining it these days, and we don't have a clear recommendation on what to write as the purpose of the guide. So this one probably isn't a good one to take.

Removing the 'help wanted' label, in case that's how you came across it. Thanks!