Add extension JS as a file to allow sourcemap detection
Add extension JS as a file to allow sourcemap detection

Fixes #1538

flarum/core,datitisev/core,datitisev/core,datitisev/core,datitisev/core,malayladu/core,malayladu/core,flarum/core,malayladu/core,flarum/core,malayladu/core