perf[Sidebar]: use sass variables in vue template

src/styles/variables.scss

@@ -12,4 +12,16 @@ $panGreen: #30B08F;
 $menuBg:#304156;
 $subMenuBg:#1f2d3d;
 $menuHover:#001528;
+$menuText:#bfcbd9;
+$menuActiveText:#409EFF;
 $sideBarWidth: 180px;
+
+// the :export directive is the magic sauce for webpack
+:export {
+  menuBg: $menuBg;
+  subMenuBg: $subMenuBg;
+  menuHover: $menuHover;
+  menuText:$menuText;
+  menuActiveText:$menuActiveText;
+  sideBarWidth: $sideBarWidth;
+}