For me it works, but I have not tried it with every exporter.
(edit: seems to be compatible with nw.js)
It gives this error: "Unable to load plugin in 'C:\Program Files\Construct 2\exporters\html5\plugins\outline\': Cannot open file 'C:\Program Files\Construct 2\exporters\html5\plugins\outline\common.js'
This plugin will not be available in the editor.
Am I putting it in the wrong folder or something? I haven't tried to install plugins before.
Why not just create your graphics with outlines?
Another option would be to use the paster object to only create outlines for the stuff on screen. Basically paste all the objects you want to have an outline to it. Make it all black by pasting a all black object to it with a blend mode. Then finally pasting it to a second object in all 8 directions.
The shader would likely be the fastest. I don't use webgl anymore so I haven't touched the effect in a while.
Well I don't want the outline to overlap with the actual graphics so they all should run in the background so I can't create them with outlines.
I will look into that other option you talked about. I'm not to experienced with any of that but I will see what I can do by myself.