Replace file extension on export

[em-c-rod]

Instead of exporting a file named my_file.json as a json and becoming my_file.json.json, I want it to just be my_file.json. The same is true, for example, when exporting a file named my_checklist.ckl to a json. I want it to be my_checklist.json instead of my_checklist.ckl.json.