onboarding: Add the AI page (#35351)

This PR starts the work on the AI onboarding page as well as the
configuration modal

Release Notes:

- N/A

---------

Co-authored-by: Danilo Leal <daniloleal09@gmail.com>
Co-authored-by: Anthony <anthony@zed.dev>

crates/ui/src/components/modal.rs

@@ -1,5 +1,5 @@
 use crate::{
-    Clickable, Color, DynamicSpacing, Headline, HeadlineSize, IconButton, IconButtonShape,
+    Clickable, Color, DynamicSpacing, Headline, HeadlineSize, Icon, IconButton, IconButtonShape,
     IconName, Label, LabelCommon, LabelSize, h_flex, v_flex,
 };
 use gpui::{prelude::FluentBuilder, *};
@@ -92,6 +92,7 @@ impl RenderOnce for Modal {
 
 #[derive(IntoElement)]
 pub struct ModalHeader {
+    icon: Option<Icon>,
     headline: Option<SharedString>,
     description: Option<SharedString>,
     children: SmallVec<[AnyElement; 2]>,
@@ -108,6 +109,7 @@ impl Default for ModalHeader {
 impl ModalHeader {
     pub fn new() -> Self {
         Self {
+            icon: None,
             headline: None,
             description: None,
             children: SmallVec::new(),
@@ -116,6 +118,11 @@ impl ModalHeader {
         }
     }
 
+    pub fn icon(mut self, icon: Icon) -> Self {
+        self.icon = Some(icon);
+        self
+    }
+
     /// Set the headline of the modal.
     ///
     /// This will insert the headline as the first item
@@ -179,12 +186,17 @@ impl RenderOnce for ModalHeader {
                 )
             })
             .child(
-                v_flex().flex_1().children(children).when_some(
-                    self.description,
-                    |this, description| {
+                v_flex()
+                    .flex_1()
+                    .child(
+                        h_flex()
+                            .gap_1()
+                            .when_some(self.icon, |this, icon| this.child(icon))
+                            .children(children),
+                    )
+                    .when_some(self.description, |this, description| {
                         this.child(Label::new(description).color(Color::Muted).mb_2())
-                    },
-                ),
+                    }),
             )
             .when(self.show_dismiss_button, |this| {
                 this.child(