chore: add legacy firefox url to the migration guide

Author: webfansplz

packages/chrome-extension/popups/vue2-migration-guide.html

@@ -7,11 +7,13 @@ <h2>Migration Tips</h2>
     Vue DevTools v7 detected in your Vue2 project. v7 only supports Vue3 and will not work.
   </p>
   <p style="text-indent: 8px">
-    The legacy version that supports both Vue 2 and Vue 3 has been moved to
+    The legacy version of chrome extension that supports both Vue 2 and Vue 3 has been moved to
     <a target="_blank" href="https://chromewebstore.google.com/detail/vuejs-devtools/iaajmlceplecbljialhhkmedjlpdblhp"
       >here</a
-    >, please install and enable only the legacy version for your Vue2 app. If you're still using v5 version, you can
-    install it
+    >
+    and the legacy version of firefox extension has been moved to
+    <a target="_blank" href="https://addons.mozilla.org/firefox/addon/vue-js-devtools-v6-legacy">here</a>, please
+    install and enable only the legacy version for your Vue2 app. If you're still using v5 version, you can install it
     <a
       target="_blank"
       href="https://chromewebstore.google.com/detail/vuejs-devtools-v5/hkddcnbhifppgmfgflgaelippbigjpjo"

packages/devtools-kit/src/core/index.ts

@@ -54,8 +54,10 @@ export function initDevTools() {
 
     console.log('%cVue DevTools v7 detected in your Vue2 project. v7 only supports Vue3 and will not work.', 'font-bold: 500; font-size: 14px;')
 
-    const url = 'https://chromewebstore.google.com/detail/vuejs-devtools/iaajmlceplecbljialhhkmedjlpdblhp'
-    console.log(`%cThe legacy version that supports both Vue 2 and Vue 3 has been moved to %c ${url}`, 'font-size: 14px;', 'text-decoration: underline; cursor: pointer;font-size: 14px;')
+    const legacyChromeUrl = 'https://chromewebstore.google.com/detail/vuejs-devtools/iaajmlceplecbljialhhkmedjlpdblhp'
+    const legacyFirefoxUrl = 'https://addons.mozilla.org/firefox/addon/vue-js-devtools-v6-legacy'
+    console.log(`%cThe legacy version of chrome extension that supports both Vue 2 and Vue 3 has been moved to %c ${legacyChromeUrl}`, 'font-size: 14px;', 'text-decoration: underline; cursor: pointer;font-size: 14px;')
+    console.log(`%cThe legacy version of firefox extension that supports both Vue 2 and Vue 3 has been moved to %c ${legacyFirefoxUrl}`, 'font-size: 14px;', 'text-decoration: underline; cursor: pointer;font-size: 14px;')
 
     console.log('%cPlease install and enable only the legacy version for your Vue2 app.', 'font-bold: 500; font-size: 14px;')