Use script_loader_src hook for temporary Categories fix

[sabernhardt]

Fixes #222

Maintains the original post handle for translations, but changes the src to the plugin's file.

[sabernhardt]

There is plenty of room for improvement :)

For example, I was lazy and did not create a name for the function.

[azaozz]

Thanks for the patch!

Moved the fix to its own function (so plugins are able to remove the filter), and prepared for release. Please have a look if it works as expected after the changes.

[jonathanbossenger]

I came here via this support thread for the Classic Editor plugin, and I can confirm that this fixes that issue as well.