Set App User Model ID on Win32

src/browser/main.coffee

@@ -13,6 +13,9 @@ start = ->
   setupCompileCache()
   return if handleStartupEventWithSquirrel()
 
+    # NB: This prevents Win10 from showing dupe items in the taskbar
+    app.setAppUserModelId('com.squirrel.atom.atom')
+
   args = parseCommandLine()
 
   addPathToOpen = (event, pathToOpen) ->