Rename iced_virtual to iced_pure

`virtual` is a reserved keyword in Rust 😬

examples/pure/counter/src/main.rs

@@ -0,0 +1,54 @@
+use iced::{Alignment, Element, Sandbox, Settings};
+use iced_pure::{Button, Column, Pure, State, Text};
+
+pub fn main() -> iced::Result {
+    Counter::run(Settings::default())
+}
+
+struct Counter {
+    value: i32,
+    state: State<Message, iced::Renderer>,
+}
+
+#[derive(Debug, Clone, Copy)]
+enum Message {
+    IncrementPressed,
+    DecrementPressed,
+}
+
+impl Sandbox for Counter {
+    type Message = Message;
+
+    fn new() -> Self {
+        Self {
+            value: 0,
+            state: State::new(),
+        }
+    }
+
+    fn title(&self) -> String {
+        String::from("Counter - Iced")
+    }
+
+    fn update(&mut self, message: Message) {
+        match message {
+            Message::IncrementPressed => {
+                self.value += 1;
+            }
+            Message::DecrementPressed => {
+                self.value -= 1;
+            }
+        }
+    }
+
+    fn view(&mut self) -> Element<'_, Message> {
+        let content = Column::new()
+            .padding(20)
+            .align_items(Alignment::Center)
+            .push(Button::new("Increment").on_press(Message::IncrementPressed))
+            .push(Text::new(self.value.to_string()).size(50))
+            .push(Button::new("Decrement").on_press(Message::DecrementPressed));
+
+        Pure::new(&mut self.state, content).into()
+    }
+}