Add wheel gestures and fix scrolling issue.

src/scss/thumbnail-carousel.scss

@@ -1,6 +1,11 @@
 :host {
   --frigate-card-carousel-thumbnail-opacity: 0.8;
+}
 
+:host([direction=vertical]) {
+  height: 100%;
+}
+:host([direction=horizontal]) {
   // In fullscreen mode, without explicitly setting the height to auto Chrome
   // will construct a stylesheet with 100% height.
   height: auto;

src/scss/timeline.scss

@@ -4,16 +4,19 @@
 :host {
   width: 100%;
   height: 100%;
-  display: block;
   background-color: var(--card-background-color);
   padding-bottom: 5px;
 
+  // Share the screen space with thumbnails that may be above/below.
+  display: flex;
+  flex-direction: column;
+
   // So that absolute sidedrawer is relative to this host.
   position: relative;
 }
 
 div.timeline {
-  height: 100%;
+  flex: 1;
 }
 div.timeline.left-margin {
   // Clearance for the drawer button.