Add seasonal effects for Pi Day, Pride, Rain, and Storm; enhance existing styles

- Introduced new CSS and JS files for Pi Day, Pride, Rain, and Storm effects.
- Updated existing seasonal styles (e.g., Halloween, Hearts, Resurrection) to improve performance with 'contain: layout paint'.
- Enhanced animations for seasonal effects, including adjustments to keyframes and element creation logic.
- Added configuration options for new effects in the main seasonals.js file.
- Updated test-site.html to include new seasonal options in the dropdown.

Jellyfin.Plugin.Seasonals/Web/carnival.css

@@ -9,13 +9,14 @@
   pointer-events: none;
   z-index: 10;
   perspective: 600px;
+  contain: layout paint;
 }
 
 .carnival-wrapper {
   position: fixed;
   z-index: 15;
   top: -20px;
-  will-change: top;
+  will-change: transform;
   animation-name: carnival-fall;
   animation-timing-function: linear;
   animation-iteration-count: 1;
@@ -59,10 +60,10 @@
 
 @keyframes carnival-fall {
   0% {
-    top: -10%;
+    transform: translateY(0);
   }
   100% {
-    top: 110%;
+    transform: translateY(120vh);
   }
 }