feat(vscode): ✨ add recommended extensions for Front Matter CMS

* Introduced a new `.vscode/extensions.json` file.
* Added recommendations for essential extensions to enhance development experience.

Author: HeyItsGilbert

.vscode/extensions.json

@@ -0,0 +1,7 @@
+{
+  "recommendations": [
+    "eliostruyf.vscode-front-matter",
+    "davidanson.vscode-markdownlint",
+    "yzhang.markdown-all-in-one",
+  ]
+}