Add an extensions installation view (#7689)

This PR adds a view for installing extensions within Zed.

My subtasks:

- [X] Page Extensions and assign in App Menu
- [X] List extensions 
- [X] Button to Install/Uninstall
- [x] Search Input to search in extensions registry API
- [x] Get Extensions from API
- [x] Action install to download extension and copy in /extensions
folder
- [x] Action uninstall to remove from /extensions folder
- [x] Filtering
- [x] Better UI Design

Open to collab!

Release Notes:

- Added an extension installation view. Open it using the `zed:
extensions` action in the command palette
([#7096](https://github.com/zed-industries/zed/issues/7096)).

---------

Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>
Co-authored-by: Marshall <marshall@zed.dev>
Co-authored-by: Carlos <foxkdev@gmail.com>
Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>
Co-authored-by: Max <max@zed.dev>

crates/zed/src/main.rs

@@ -173,7 +173,13 @@ fn main() {
         );
         assistant::init(cx);
 
-        extension::init(fs.clone(), languages.clone(), ThemeRegistry::global(cx), cx);
+        extension::init(
+            fs.clone(),
+            http.clone(),
+            languages.clone(),
+            ThemeRegistry::global(cx),
+            cx,
+        );
 
         load_user_themes_in_background(fs.clone(), cx);
         #[cfg(target_os = "macos")]
@@ -254,6 +260,7 @@ fn main() {
         feedback::init(cx);
         markdown_preview::init(cx);
         welcome::init(cx);
+        extensions_ui::init(cx);
 
         cx.set_menus(app_menus());
         initialize_workspace(app_state.clone(), cx);