[core] Add VSCode extensions recommendations (mui#37166)

Author: michaldudak

.gitignore

@@ -6,6 +6,7 @@
 *.iml
 .vscode/*
 !.vscode/launch.json
+!.vscode/extensions.json
 *.log
 *.tsbuildinfo
 /.eslintcache

.vscode/extensions.json

@@ -0,0 +1,9 @@
+{
+  "recommendations": [
+    "editorconfig.editorconfig",
+    "dbaeumer.vscode-eslint",
+    "davidanson.vscode-markdownlint",
+    "esbenp.prettier-vscode",
+    "yoavbls.pretty-ts-errors"
+  ]
+}