Fixes width of sidepanel

src/editor/js/components/editor.css

@@ -8,7 +8,7 @@ div#ks-editor #sidepanel {
     /* resize: horizontal; */
     overflow: auto;
     min-width: 300px;
-    max-width: 40%;
+    max-width: 20%;
     height: inherit;
     margin: 0.3rem;
     margin-right: 0.3rem;