Import will try importing non-relative .json files

[mundusnine]

Issue:
If developping with rust or if using Tiled .json files the importer will try importing these files and will fail. Even if the import failed with these json's it always tries to reimport when exiting godot focus and taking back focus.

Solutions:
1 - Adding options to remove checking in some paths
or
2 - Changing the import type to be .spck and asking users to rename the json file with that extension( essentially it's a bogus extension and the data in the file is still json).