feat: Implement basic general folder support (#2051)

- Related: #1748

src/scss/thumbnail-feature.scss

@@ -0,0 +1,69 @@
+:host {
+  display: flex;
+  flex-direction: column;
+  justify-content: space-evenly;
+  align-items: center;
+
+  max-width: var(--advanced-camera-card-thumbnail-size);
+  max-height: var(--advanced-camera-card-thumbnail-size);
+
+  aspect-ratio: 1 / 1;
+
+  border: 1px solid var(--secondary-color);
+  background-color: var(--secondary-background-color);
+  border-radius: var(
+    --advanced-camera-card-css-border-radius,
+    var(--ha-card-border-radius, 4px)
+  );
+
+  box-sizing: border-box;
+
+  // Background icon relative to the thumbnail.
+  position: relative;
+}
+
+advanced-camera-card-thumbnail-feature-thumbnail {
+  height: 50%;
+}
+advanced-camera-card-thumbnail-feature-thumbnail.brand:only-child {
+  height: 60%;
+}
+advanced-camera-card-thumbnail-feature-thumbnail:not(.brand):only-child {
+  height: 100%;
+}
+
+advanced-camera-card-icon:only-child {
+  width: 60%;
+  height: 60%;
+
+  --mdc-icon-size: 100%;
+}
+
+advanced-camera-card-icon.background {
+  display: block;
+  width: 100%;
+  height: 100%;
+
+  position: absolute;
+  inset: 0;
+
+  padding: 10%;
+  box-sizing: border-box;
+
+  pointer-events: none;
+
+  opacity: 0.1;
+
+  --mdc-icon-size: 100%;
+}
+
+div {
+  text-align: center;
+  color: var(--primary-text-color);
+}
+div.title {
+  font-size: 1.5rem;
+}
+div.subtitle {
+  font-size: 0.8em;
+}