GP: Fix Merge By Distance

There's this issue where strokes which overlap eachother can cause this annoying color fill bleeding issue: This could be a simple fix by using the simplify modifier but the issue is that GP's simplify>merge modifier only merges vertices that are connected to eachother and ignores vertices that have been drawn on later. (can see that the simplify>merge modifier has no effect on the center vertz)

Solution:

Add a "Mode" option to the Simplify modifier like the Weld modifier has where you can pick between All or Connected as merging options