Add TrafficLights component (#3011)

This PR adds a `TrafficLights` component for GPUI2.

<img width="861" alt="Screenshot 2023-09-21 at 11 32 10 PM"
src="https://github.com/zed-industries/zed/assets/1486634/0fe0e847-49b3-44dc-bd4c-64f12f0051c1">

Release Notes:

- N/A

crates/storybook/src/stories/components.rs

@@ -1 +1,2 @@
 pub mod facepile;
+pub mod traffic_lights;

crates/storybook/src/stories/components/traffic_lights.rs

@@ -0,0 +1,29 @@
+use gpui2::elements::div;
+use gpui2::style::StyleHelpers;
+use gpui2::{rgb, Element, Hsla, IntoElement, ParentElement, ViewContext};
+use ui::{theme, traffic_lights};
+
+#[derive(Element, Default)]
+pub struct TrafficLightsStory {}
+
+impl TrafficLightsStory {
+    fn render<V: 'static>(&mut self, _: &mut V, cx: &mut ViewContext<V>) -> impl IntoElement<V> {
+        let theme = theme(cx);
+
+        div()
+            .size_full()
+            .flex()
+            .flex_col()
+            .pt_2()
+            .px_4()
+            .font("Zed Mono Extended")
+            .fill(rgb::<Hsla>(0x282c34))
+            .child(
+                div()
+                    .text_2xl()
+                    .text_color(rgb::<Hsla>(0xffffff))
+                    .child(std::any::type_name::<ui::TrafficLights>()),
+            )
+            .child(traffic_lights())
+    }
+}

crates/storybook/src/storybook.rs

@@ -14,6 +14,7 @@ use log::LevelFilter;
 use settings::{default_settings, SettingsStore};
 use simplelog::SimpleLogger;
 use stories::components::facepile::FacepileStory;
+use stories::components::traffic_lights::TrafficLightsStory;
 use stories::elements::avatar::AvatarStory;
 use ui::{ElementExt, Theme};
 
@@ -35,6 +36,7 @@ impl FromStr for Story {
         match s.to_ascii_lowercase().as_str() {
             "elements/avatar" => Ok(Self::Element(ElementStory::Avatar)),
             "components/facepile" => Ok(Self::Component(ComponentStory::Facepile)),
+            "components/traffic_lights" => Ok(Self::Component(ComponentStory::TrafficLights)),
             _ => Err(anyhow!("story not found for '{s}'")),
         }
     }
@@ -48,6 +50,7 @@ enum ElementStory {
 #[derive(Debug, Clone, Copy)]
 enum ComponentStory {
     Facepile,
+    TrafficLights,
 }
 
 #[derive(Parser)]
@@ -82,6 +85,9 @@ fn main() {
                 Some(Story::Component(ComponentStory::Facepile)) => {
                     view(|cx| render_story(&mut ViewContext::new(cx), FacepileStory::default()))
                 }
+                Some(Story::Component(ComponentStory::TrafficLights)) => view(|cx| {
+                    render_story(&mut ViewContext::new(cx), TrafficLightsStory::default())
+                }),
                 None => {
                     view(|cx| render_story(&mut ViewContext::new(cx), WorkspaceElement::default()))
                 }