Upsell built-in features on the extensions page (#14516)

This PR extends the extensions page with support for upselling built-in
Zed features when certain keywords are searched for.

This should help inform users about features that Zed has out-of-the-box
when they go looking for them as extensions.

For example, when someone searches "vim":

<img width="1341" alt="Screenshot 2024-07-15 at 4 58 44 PM"
src="https://github.com/user-attachments/assets/b256d07a-559a-43c2-b491-3eca5bff436e">

Here are more examples of what the upsells can look like:

<img width="1341" alt="Screenshot 2024-07-15 at 4 54 39 PM"
src="https://github.com/user-attachments/assets/1f453132-ac14-4884-afc4-7c12db47ad1d">

Release Notes:

- Added banners for built-in Zed features when corresponding keywords
are used in the extension search.

crates/gpui_macros/src/styles.rs

@@ -353,7 +353,7 @@ pub fn border_style_methods(input: TokenStream) -> TokenStream {
         /// Sets the border color of the element.
         #visibility fn border_color<C>(mut self, border_color: C) -> Self
         where
-            C: Into<Hsla>,
+            C: Into<gpui::Hsla>,
             Self: Sized,
         {
             self.style().border_color = Some(border_color.into());