feat: Initial devtools support (#1125)

packages/vue/src/dev.ts

@@ -0,0 +1,16 @@
+import { version, setDevtoolsHook } from '@vue/runtime-dom'
+
+export function initDev() {
+  const target: any = __BROWSER__ ? window : global
+
+  target.__VUE__ = version
+  setDevtoolsHook(target.__VUE_DEVTOOLS_GLOBAL_HOOK__)
+
+  if (__BROWSER__) {
+    // @ts-ignore `console.info` cannot be null error
+    console[console.info ? 'info' : 'log'](
+      `You are running a development build of Vue.\n` +
+        `Make sure to use the production build (*.prod.js) when deploying for production.`
+    )
+  }
+}