Add section about Debputy
NOTE! @osamu Please do not rush to merge this, but instead provide feedback and allow some time for the change to be polished. If you have no feedback, you may mark the Merge Request approved. If you are using Salsa via command-line, you can do it with glab mr approve 30.
Ready to be merged if approved.
From commit message:
Present Debputy to readers in the same context that explains the files in debian/* to encourage readers to use it to validate correctness of the files while or after editing them.
Edited by Otto Kekäläinen