Simple velocity example

src/style.rs

@@ -139,12 +139,19 @@ impl Transform {
     }
 
     /// Sets constant dimensions.
-    pub fn dimensions(mut self, width: u16, height: u16) -> Self {
+    pub fn dimensions_const(mut self, width: u16, height: u16) -> Self {
         self.width = Dimension::Const(width);
         self.height = Dimension::Const(height);
         self
     }
 
+    /// Sets constant dimensions.
+    pub fn dimensions(mut self, width: Dimension, height: Dimension) -> Self {
+        self.width = width;
+        self.height = height;
+        self
+    }
+
     /// Resolves `Dimension` rules into absolute values for the given parent size.
     pub fn use_dimensions(&self, parent_transform: &RawTransform, raw: &mut RawTransform) {
         self.width