Scaffold Toolbar and Breadcrumb components (#3020)

This PR scaffolds the `Toolbar` and `Breadcrumb` components.

Right now they both just consist of hardcoded data.

<img width="846" alt="Screenshot 2023-09-22 at 4 54 00 PM"
src="https://github.com/zed-industries/zed/assets/1486634/70578df2-7216-42d2-97ef-d38b83fb4a25">

<img width="799" alt="Screenshot 2023-09-22 at 4 46 04 PM"
src="https://github.com/zed-industries/zed/assets/1486634/73ca3d8a-baf9-4ed4-b4c4-279c674672a3">

Release Notes:

- N/A

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

@@ -0,0 +1,16 @@
+use gpui2::{Element, IntoElement, ParentElement, ViewContext};
+use ui::toolbar;
+
+use crate::story::Story;
+
+#[derive(Element, Default)]
+pub struct ToolbarStory {}
+
+impl ToolbarStory {
+    fn render<V: 'static>(&mut self, _: &mut V, cx: &mut ViewContext<V>) -> impl IntoElement<V> {
+        Story::container()
+            .child(Story::title_for::<_, ui::Toolbar>())
+            .child(Story::label("Default"))
+            .child(toolbar())
+    }
+}