modified error messages. updated manifest ver from 4 to 3

Author: EivindDelFierro

src/app/components/ErrorMsg.tsx

@@ -31,10 +31,12 @@ function ErrorMsg({ loadingArray, status, launchContent }): JSX.Element {
     case 'Content Script Error':
       return (
         <div>
-          If you encounter this error on the initial launch of Reactime, refresh the webpage you are developing.
+          Could not connect to the Target App. Try closing Reactime and reloading the page.
           <br />
           <br />
-          Could not connect to the Target App. Try closing Reactime and reloading the page.
+          If you encounter this error on the initial launch of Reactime, refresh the webpage you are developing. 
+          <br />
+          If Reactime is running as an iframe in your developer tools, right click on the Reactime application and click 'Reload Frame'
           <br />
           <br />
           NOTE: By default Reactime only launches the content script on URLS starting with
@@ -52,10 +54,12 @@ function ErrorMsg({ loadingArray, status, launchContent }): JSX.Element {
     case 'RDT Error':
       return (
         <div>
-          If you encounter this error on the initial launch of Reactime, refresh the webpage you are developing.
+          React Dev Tools is not installed!
+          <br />
           <br />
+          If you encounter this error on the initial launch of Reactime, refresh the webpage you are developing. 
           <br />
-          React Dev Tools isnt installed!
+          If Reactime is running as an iframe in your developer tools, right click on the Reactime application and click 'Reload Frame'
           <br />
           <br />
           <a

src/extension/build/manifest.json

@@ -3,7 +3,7 @@
   "version": "21.0.0",
   "devtools_page": "devtools.html",
   "description": "A Chrome extension that helps debug React applications by memorizing the state of components with every render.",
-  "manifest_version": 4,
+  "manifest_version": 3,
   "background": {
     "service_worker": "bundles/background.bundle.js"
   },