build(multiple): recommend installing the bazel extension

Since the repo uses Bazel, installing the Bazel extension will give syntax highlighting and other features

Author: jermowery

.vscode/extensions.json

@@ -6,6 +6,7 @@
   "recommendations": [
     "ms-vscode.vscode-typescript-tslint-plugin",
     "esbenp.prettier-vscode",
-    "angular.ng-template"
+    "angular.ng-template",
+    "bazelbuild.vscode-bazel"
   ]
 }