Update version to v0.1.2.a.3 and enhance UI/UX features

- Updated version number in version.txt.
- Improved smooth scrolling for anchor links in script.js.
- Added Intersection Observer for fade-in animations in script.js.
- Enhanced CSS styles for various elements, including buttons, metrics, and backgrounds for better visual appeal and interactivity.

index.html

@@ -45,7 +45,7 @@
     <div class="hero__metrics">
       <div class="metric">
         <p class="metric__label">Current release</p>
-        <p class="metric__value">v0.1.2.a.2</p>
+        <p class="metric__value">v0.1.2.a.3</p>
       </div>
       <div class="metric">
         <p class="metric__label">Supported families</p>