* Allow for relative paths of media files
fixes#325
* Switch to calculating the relative path based on collection
The required relative path is now calculated depending on the
location of the collection of the current entry having the
media inserted into. And the configuration option has now been
changed to a boolean flag.
This allows collections to not neccesarily all be in the same
location relative to the media folder, and simplifies config.
* Clean up code and fix linting
* Add unit tests to resolveMediaFilename()
* Rework insertMedia action to fetch own config
This moves more of the media path resolution logic into the action
which makes it easier to unit test
* Add unit tests for the mediaLibrary.insertMedia action
* yarn run format
* add dependabot config (#2580)
