Refactor ruin_app, add some README files, minor usability in reactivity

lib/ruin_app/src/converters.rs

@@ -0,0 +1,43 @@
+use ruin_ui::{Border, BoxShadow, Color, Edges};
+
+pub trait IntoEdges {
+    fn into_edges(self) -> Edges;
+}
+
+impl IntoEdges for Edges {
+    fn into_edges(self) -> Edges {
+        self
+    }
+}
+
+impl IntoEdges for f32 {
+    fn into_edges(self) -> Edges {
+        Edges::all(self)
+    }
+}
+
+pub trait IntoBorder {
+    fn into_border(self) -> Border;
+}
+
+impl IntoBorder for Border {
+    fn into_border(self) -> Border {
+        self
+    }
+}
+
+impl IntoBorder for (f32, Color) {
+    fn into_border(self) -> Border {
+        Border::new(self.0, self.1)
+    }
+}
+
+pub trait IntoShadow {
+    fn into_shadow(self) -> BoxShadow;
+}
+
+impl IntoShadow for BoxShadow {
+    fn into_shadow(self) -> BoxShadow {
+        self
+    }
+}