Add Quick Collapse extension (#71)

* Add Quick Collapse extension

* Remove async for JS scripts

* Homogeneize const declarations in script

extensions.json

@@ -184,6 +184,15 @@
       "author": "Alexis Degrugillier",
       "url": "https://github.com/aledeg/FreshRSS-extensions",
       "type": "gh-subdirectory"
+    },
+    {
+      "name": "Quick Collapse",
+      "description": "Improve the sharing by email system.",
+      "description": "Quickly change from folded to unfolded articles",
+      "version": 0.1,
+      "author": "romibi and Marien Fressinaud",
+      "url": "https://github.com/FreshRSS/Extensions",
+      "type": "gh-subdirectory"
     }
   ]
 }