add styles for the skeleton and shimmer components

frontend/src/styles/skeleton.css

@@ -0,0 +1,70 @@
+.skeleton {
+    display: flex;
+    flex-flow: column nowrap;
+    background: #ddd;
+    margin: 10px 0;
+    overflow: hidden;
+}
+
+.skeleton-product-wrapper {
+    position: relative;
+    margin-top: 1em;
+    background: #c0c0c0;
+    border-radius: 10px;
+    padding: 0.5em;
+    overflow: hidden;
+}
+
+.skeleton.box {
+    height: 25ch;
+    width: 100%;
+}
+
+.skeleton-product-wrapper .skeleton.box {
+    margin-top: 0;
+    margin-bottom: 10%;
+    border-radius: 10px 10px 0 0;
+}
+
+.skeleton.title {
+    height: 3ch;
+}
+
+.skeleton.text {
+    width: 100%;
+    height: 2ch;
+    margin: 1em 0;
+}
+
+/* for the animations */
+
+.shimmer-wrapper {
+    position: absolute;
+    top: 0;
+    bottom: 0;
+    width: 100%;
+    height: 100%;
+    animation: loading 2s infinite;
+}
+
+.shimmer {
+    width: 50%;
+    height: 100%;
+    background: rgba(255, 255, 255, 0.3);
+    transform: skewX(-20deg);
+    box-shadow: 0 0 30px 10px rgba(255, 255, 255, 0.05);
+}
+
+@keyframes loading {
+    0% {
+        transform: translateX(-150%);
+    }
+
+    50% {
+        transform: translateX(50%);
+    }
+
+    100% {
+        transform: translateX(150%);
+    }
+}