feat: add remotion-best-practices skill from remotion-dev/skills

Imported official Remotion skill for video creation in React:
- 28 modular rule files covering animations, audio, video, captions, 3D, etc.
- Added author (remotion-dev) and version (1.0) metadata
- Updated skill count: 224 → 225
- Regenerated skills_index.json

Source: https://github.com/remotion-dev/skills

skills/remotion-best-practices/rules/animations.md

@@ -0,0 +1,29 @@
+---
+name: animations
+description: Fundamental animation skills for Remotion
+metadata:
+  tags: animations, transitions, frames, useCurrentFrame
+---
+
+All animations MUST be driven by the `useCurrentFrame()` hook.  
+Write animations in seconds and multiply them by the `fps` value from `useVideoConfig()`.
+
+```tsx
+import { useCurrentFrame } from "remotion";
+
+export const FadeIn = () => {
+  const frame = useCurrentFrame();
+  const { fps } = useVideoConfig();
+
+  const opacity = interpolate(frame, [0, 2 * fps], [0, 1], {
+    extrapolateRight: 'clamp',
+  });
+ 
+  return (
+    <div style={{ opacity }}>Hello World!</div>
+  );
+};
+```
+
+CSS transitions or animations are FORBIDDEN - they will not render correctly.  
+Tailwind animation class names are FORBIDDEN - they will not render correctly.