Move widgets from core to native and web

Also made fields private and improved `Renderer` traits.

web/src/widget/radio.rs

@@ -1,8 +1,71 @@
-use crate::{Bus, Element, Widget};
+use crate::{Bus, Color, Element, Widget};
 
 use dodrio::bumpalo;
 
-pub use iced_core::Radio;
+/// A circular button representing a choice.
+///
+/// # Example
+/// ```
+/// # use iced_web::Radio;
+///
+/// #[derive(Debug, Clone, Copy, PartialEq, Eq)]
+/// pub enum Choice {
+///     A,
+///     B,
+/// }
+///
+/// #[derive(Debug, Clone, Copy)]
+/// pub enum Message {
+///     RadioSelected(Choice),
+/// }
+///
+/// let selected_choice = Some(Choice::A);
+///
+/// Radio::new(Choice::A, "This is A", selected_choice, Message::RadioSelected);
+///
+/// Radio::new(Choice::B, "This is B", selected_choice, Message::RadioSelected);
+/// ```
+///
+/// ![Radio buttons drawn by Coffee's renderer](https://github.com/hecrj/coffee/blob/bda9818f823dfcb8a7ad0ff4940b4d4b387b5208/images/ui/radio.png?raw=true)
+pub struct Radio<Message> {
+    is_selected: bool,
+    on_click: Message,
+    label: String,
+    label_color: Option<Color>,
+}
+
+impl<Message> Radio<Message> {
+    /// Creates a new [`Radio`] button.
+    ///
+    /// It expects:
+    ///   * the value related to the [`Radio`] button
+    ///   * the label of the [`Radio`] button
+    ///   * the current selected value
+    ///   * a function that will be called when the [`Radio`] is selected. It
+    ///   receives the value of the radio and must produce a `Message`.
+    ///
+    /// [`Radio`]: struct.Radio.html
+    pub fn new<F, V>(value: V, label: &str, selected: Option<V>, f: F) -> Self
+    where
+        V: Eq + Copy,
+        F: 'static + Fn(V) -> Message,
+    {
+        Radio {
+            is_selected: Some(value) == selected,
+            on_click: f(value),
+            label: String::from(label),
+            label_color: None,
+        }
+    }
+
+    /// Sets the `Color` of the label of the [`Radio`].
+    ///
+    /// [`Radio`]: struct.Radio.html
+    pub fn label_color<C: Into<Color>>(mut self, color: C) -> Self {
+        self.label_color = Some(color.into());
+        self
+    }
+}
 
 impl<Message> Widget<Message> for Radio<Message>
 where