Add a couple trivial const fn conversions

src/base/dimension.rs

@@ -20,7 +20,7 @@ pub struct Dynamic {
 impl Dynamic {
     /// A dynamic size equal to `value`.
     #[inline]
-    pub fn new(value: usize) -> Self {
+    pub const fn new(value: usize) -> Self {
         Self { value }
     }
 }

src/base/unit.rs

@@ -221,7 +221,7 @@ impl<T: Normed> Unit<T> {
 impl<T> Unit<T> {
     /// Wraps the given value, assuming it is already normalized.
     #[inline]
-    pub fn new_unchecked(value: T) -> Self {
+    pub const fn new_unchecked(value: T) -> Self {
         Unit { value }
     }