Re-add the "Manage Libraries..." item in its old place

Now "Manage Libraries" is available in its old place too (Sketch → Include Libraries → *Manage Libraries...*)

Please note that this commit makes this item duplicated in the menu, because it's also available in "Tools → *Manage Libraries...*"

Author: feikname

Diff for: app/src/processing/app/Base.java

@@ -1069,7 +1069,9 @@ public void rebuildImportMenu(JMenu importMenu) {
       return;
     importMenu.removeAll();
 
-    // Historical note: "Manage Libraries..." used to go here before v1.9.0
+    JMenuItem menu = new JMenuItem(tr("Manage Libraries..."));
+    menu.addActionListener(e -> openLibraryManager("", ""));
+    importMenu.add(menu);
 
     importMenu.addSeparator();