Updated ad placeholder graphics, update Modrinth App sidebar to mockup designs (#4584)

* Update ad placeholders to new green graphic

* Remove rounded corners from app ad frame

* Improve web ad placeholder styling

* Revamp app sidebar to match mockups more closely, greatly improve friends UX, fix up context menus and typify shit

* only show overflow on hover

* lint

* intl:extract

* clean up the inline code in FriendsSection

packages/ui/src/locales/en-US/index.json

@@ -17,6 +17,9 @@
   "button.cancel": {
     "defaultMessage": "Cancel"
   },
+  "button.clear": {
+    "defaultMessage": "Clear"
+  },
   "button.close": {
     "defaultMessage": "Close"
   },