Add an app button (so its possible open the Outliner directly without opening any windows)

I think it would be interesting to add an shortcut on desktop to Tabs Outliner, so that we can open it directly, without opening an window first and then clicking the extension icon.

I've managed to to this by running

google-chrome --app="chrome-extension://eggkanocgddhmamlbiijnphhppkpkmkl/activesessionview.html"

but that's not much user friendly.