add cache and loader for big menu

src/SideMenuBig.vue

@@ -23,6 +23,25 @@ along with this program. If not, see <http://www.gnu.org/licenses/>.
 
         <div class="side-menu-categories-wrapper">
             <div class="side-menu-categories">
+                <div v-if="!items.length" class="side-menu-loader">
+                    <svg width="38" height="38" viewBox="0 0 38 38" xmlns="http://www.w3.org/2000/svg">
+                        <g fill="none" fill-rule="evenodd">
+                            <g transform="translate(1 1)" stroke-width="2">
+                                <circle stroke-opacity=".5" cx="18" cy="18" r="18"/>
+                                <path d="M36 18c0-9.94-8.06-18-18-18">
+                                    <animateTransform
+                                        attributeName="transform"
+                                        type="rotate"
+                                        from="0 18 18"
+                                        to="360 18 18"
+                                        dur="1s"
+                                        repeatCount="indefinite"/>
+                                </path>
+                            </g>
+                        </g>
+                    </svg>
+                </div>
+
                 <div class="side-menu-category" v-for="category in items">
                     <h2 class="side-menu-category-title" v-if="category.name != ''" v-html="category.name"></h2>