Brackets Spring 22 changes getIndentUnit to getSpaceUnits

As noted in the Brackets Spring 22 [Release Notes](https://github.com/adobe/brackets/wiki/Release-Notes:-Sprint-22), the ```Editor.getIndentUnit/Editor.setIndentUnit``` api has been replaced with ```Editor.getSpaceUnits/Editor.setSpaceUnits```.

This change fixes the extension for brackets going forward without breaking backwards compatibility.