chore: add support for antigravity external app protocol (#20873)

Adds `antigravity` to the allowed protocols list.

Related PR:
coder/registry#558

(cherry picked from commit 8e0516a)

Author: DevelopmentCats

site/src/modules/apps/apps.ts

@@ -24,6 +24,7 @@ const ALLOWED_EXTERNAL_APP_PROTOCOLS = [
 	"jetbrains:",
 	"kiro:",
 	"positron:",
+	"antigravity:",
 ];
 
 type GetVSCodeHrefParams = {