Server: Files App plugin that opens ownNote when edit is clicked for a note in the Notes folder

ownNotes saves all created notes as html files in the notes folder of ownCloud. If this directory is accessed from the files menu all files could be edited as pure html files. It would be nice if the ownNotes app would be automatically used to open this files if they're directly accessed from that folder, instead of the default html editor.
## Environment

ownCloud v8.0.4
ownNotes v1.0

No files or tests are named. Start by reviewing how ownNotes stores HTML files in the Notes folder and how the ownCloud Files menu selects an editor for direct file edits. Done means files opened from that folder launch ownNotes instead of the default HTML editor.

Written by the indexing model from the issue text.