Add Renderer::Defaults and style inheritance

wgpu/src/defaults.rs

@@ -0,0 +1,27 @@
+use iced_native::Color;
+
+#[derive(Debug, Clone, Copy)]
+pub struct Defaults {
+    pub text: Text,
+}
+
+impl Default for Defaults {
+    fn default() -> Defaults {
+        Defaults {
+            text: Text::default(),
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+pub struct Text {
+    pub color: Color,
+}
+
+impl Default for Text {
+    fn default() -> Text {
+        Text {
+            color: Color::BLACK,
+        }
+    }
+}