Add editorconfig to recommended extensions (#2922)

Author: xtqqczze

.vscode/extensions.json

@@ -2,6 +2,7 @@
   // See http://go.microsoft.com/fwlink/?LinkId=827846
   // for the documentation about the extensions.json format
   "recommendations": [
+    "editorconfig.editorconfig",
     "msjsdiag.debugger-for-chrome",
     "ms-vscode.powershell",
     "ms-vscode.vscode-typescript-tslint-plugin",