Implement From<Vec2> for AspectRatio (#12754)

# Objective
Since it is common to store a pair of width and height as `Vec2`, it
would be useful to have an easy way to instantiate `AspectRatio` from
`Vec2`.

## Solution
Add `impl From<Vec2> for AspectRatio`.

---

## Changelog
- Added `impl From<Vec2> for AspectRatio`

crates/bevy_math/src/aspect_ratio.rs

@@ -1,5 +1,7 @@
 //! Provides a simple aspect ratio struct to help with calculations.
 
+use crate::Vec2;
+
 /// An `AspectRatio` is the ratio of width to height.
 pub struct AspectRatio(f32);
 
@@ -17,6 +19,13 @@ impl AspectRatio {
     }
 }
 
+impl From<Vec2> for AspectRatio {
+    #[inline]
+    fn from(value: Vec2) -> Self {
+        Self::new(value.x, value.y)
+    }
+}
+
 impl From<AspectRatio> for f32 {
     #[inline]
     fn from(aspect_ratio: AspectRatio) -> Self {