feat: Add loading spinner on card initialization (#1549)

* feat: Add loading spinner on card initialization

* Minor doc fix.

src/scss/card.scss

@@ -13,6 +13,7 @@
   border-radius: var(--ha-card-border-radius, 4px);
 
   height: var(--frigate-card-height);
+  min-height: 100px;
 
   // Ensure all clicks at the top level work.
   pointer-events: all;
@@ -29,6 +30,12 @@
   --frigate-card-height: auto;
 }
 
+frigate-card-loading {
+  position: absolute;
+  inset: 0;
+  z-index: 1;
+}
+
 :host([dark]) {
   filter: brightness(75%);
 }

src/scss/loading.scss

@@ -0,0 +1,40 @@
+:host {
+  height: 100%;
+  width: 100%;
+
+  display: flex;
+  justify-content: center;
+  align-items: center;
+
+  pointer-events: none;
+
+  transition: opacity 1s;
+}
+
+:host([show]) {
+  opacity: 1;
+}
+
+:host(:not([show])) {
+  opacity: 0;
+}
+
+img {
+  width: 40%;
+  height: 40%;
+
+  opacity: 0.2;
+
+  filter: invert(100%);
+
+  animation: rotate 8s linear infinite;
+}
+
+@keyframes rotate {
+  from {
+    transform: rotate(0deg);
+  }
+  to {
+    transform: rotate(360deg);
+  }
+}