Thanks to the Treyarch PC development team we now have our own GSC syntax for Sublime Text 3! Another thing is that it is fairly easy to install.
Make sure that you installed the BO3 modtools and that they are up-to-date! This ensures that you are installing the latest version!
The GSC package contains some useful tools to make BO3 scripting easier and more convenient.
Some of these functions are:
This package is located in root/docs_modtools.
Here you will find a zip-file named "gsc_sublime.zip". Once located you will want to extract the files contents into a folder called GSC / What ever you want. This part is not that important but the contents of that ".zip" must go into a folder. Now copy that folder you have created ( the folder & its contents are now saved into your clipboard ).
Next navigate to your Sublime Text 3 root directory. This can be done easily by launching Sublime Text 3, going to "Preferences" (Top bar) and clicking on "Browse Packages". Your packages folder will now open. Paste your folder in there. You're done!
Now you can restart Sublime Text (if it was still open) and in the bottom right you should be able to select GSC from the list!
Credits: Tustin(Creator) & Lukkie1998(Doc converter)