Add "transparent" doc alias for Color::NONE (#7160)

As mentioned in #6530. It allows to not create a new constant and simply having it to show up in the documentation when someone is looking for "transparent" (case insensitive) in rustdoc search.

cc @alice-i-cecile

Author: GuillaumeGomez

crates/bevy_render/src/color/mod.rs

@@ -91,6 +91,7 @@ impl Color {
     /// <div style="background-color:rgb(0%, 0%, 50%); width: 10px; padding: 10px; border: 1px solid;"></div>
     pub const NAVY: Color = Color::rgb(0.0, 0.0, 0.5);
     /// <div style="background-color:rgba(0%, 0%, 0%, 0%); width: 10px; padding: 10px; border: 1px solid;"></div>
+    #[doc(alias = "transparent")]
     pub const NONE: Color = Color::rgba(0.0, 0.0, 0.0, 0.0);
     /// <div style="background-color:rgb(50%, 50%, 0%); width: 10px; padding: 10px; border: 1px solid;"></div>
     pub const OLIVE: Color = Color::rgb(0.5, 0.5, 0.0);