feat(Sky): Configure Open VSX extension gallery

Populate the extensionsGallery configuration in product.json with Open VSX marketplace endpoints. This enables the extension browsing and installation functionality in the editor, allowing users to discover and install extensions from the open-source Open VSX registry.

Author: NikolaRHristov

Public/product.json

@@ -18,9 +18,9 @@
 	"extensionAllowedProposedApi": [],
 	"builtInExtensions": [],
 	"extensionsGallery": {
-		"serviceUrl": "",
-		"itemUrl": "",
-		"resourceUrlTemplate": ""
+		"serviceUrl": "https://open-vsx.org/api",
+		"itemUrl": "https://open-vsx.org/extension",
+		"resourceUrlTemplate": "https://open-vsx.org/files/{publisher}/{name}/{version}/{path}"
 	},
 	"documentationUrl": "https://editor.land",
 	"introductoryVideosUrl": "",