feat(overmind): add error message for devtools issue

Author: christianalfoni

packages/node_modules/overmind/src/Devtools.ts

@@ -1,5 +1,5 @@
-import { IS_PROXY } from 'proxy-state-tree'
 import isPlainObject from 'is-plain-obj'
+import { IS_PROXY } from 'proxy-state-tree'
 
 export type Message = {
   type: string
@@ -59,7 +59,16 @@ export class Devtools {
       this.isConnected = true
       this.sendBuffer()
     }
-    this.ws.onerror = () => {}
+    this.ws.onerror = () => {
+      console.error(
+        `OVERMIND DEVTOOLS: Not able to connect. You are trying to connect to "${host}", but there was no devtool there. Try the following:
+        
+          - Make sure you are running the latest version of the devtools, using "npx overmind-devtools@latest" or install latest extension for VSCode
+          - Close the current tab and open a new one
+          - Make sure the correct port is configured in the devtools
+        `
+      )
+    }
     this.ws.onclose = () => {
       this.isConnected = false