docs: update v8 docs links to point to legacy site (#2227)

Author: babu-ch

docs/guide/extra/v8-docs.md

@@ -1,22 +1,22 @@
 # Documentation for v8.x
 
-- [Introduction](https://github.com/intlify/vue-i18n/blob/master/docs-old/introduction.md)
-- [Getting started](https://github.com/intlify/vue-i18n/blob/master/docs-old/started.md)
-- [Installation](https://github.com/intlify/vue-i18n/blob/master/docs-old/installation.md)
+- [Introduction](https://kazupon.github.io/vue-i18n/introduction.html)
+- [Getting started](https://kazupon.github.io/vue-i18n/started.html)
+- [Installation](https://kazupon.github.io/vue-i18n/installation.html)
 - Guide
-  - [Formatting](https://github.com/intlify/vue-i18n/blob/master/docs-old/guide/formatting.md)
-  - [Pluralization](https://github.com/intlify/vue-i18n/blob/master/docs-old/guide/pluralization.md)
-  - [DateTime localization](https://github.com/intlify/vue-i18n/blob/master/docs-old/guide/datetime.md)
-  - [Number localization](https://github.com/intlify/vue-i18n/blob/master/docs-old/guide/number.md)
-  - [Locale messages syntax](https://github.com/intlify/vue-i18n/blob/master/docs-old/guide/messages.md)
-  - [Fallback localization](https://github.com/intlify/vue-i18n/blob/master/docs-old/guide/fallback.md)
-  - [Component based localization](https://github.com/intlify/vue-i18n/blob/master/docs-old/guide/component.md)
-  - [Custom directive localization](https://github.com/intlify/vue-i18n/blob/master/docs-old/guide/directive.md)
-  - [Component interpolation](https://github.com/intlify/vue-i18n/blob/master/docs-old/guide/interpolation.md)
-  - [Single file components](https://github.com/intlify/vue-i18n/blob/master/docs-old/guide/sfc.md)
-  - [Hot reloading](https://github.com/intlify/vue-i18n/blob/master/docs-old/guide/hot-reload.md)
-  - [Locale changing](https://github.com/intlify/vue-i18n/blob/master/docs-old/guide/locale.md)
-  - [Lazy loading translations](https://github.com/intlify/vue-i18n/blob/master/docs-old/guide/lazy-loading.md)
-  - [Tooling](https://github.com/intlify/vue-i18n/blob/master/docs-old/guide/tooling.md)
-- [API references](https://github.com/intlify/vue-i18n/blob/master/docs-old/api/README.md)
+  - [Formatting](https://kazupon.github.io/vue-i18n/guide/formatting.html)
+  - [Pluralization](https://kazupon.github.io/vue-i18n/guide/pluralization.html)
+  - [DateTime localization](https://kazupon.github.io/vue-i18n/guide/datetime.html)
+  - [Number localization](https://kazupon.github.io/vue-i18n/guide/number.html)
+  - [Locale messages syntax](https://kazupon.github.io/vue-i18n/guide/messages.html)
+  - [Fallback localization](https://kazupon.github.io/vue-i18n/guide/fallback.html)
+  - [Component based localization](https://kazupon.github.io/vue-i18n/guide/component.html)
+  - [Custom directive localization](https://kazupon.github.io/vue-i18n/guide/directive.html)
+  - [Component interpolation](https://kazupon.github.io/vue-i18n/guide/interpolation.html)
+  - [Single file components](https://kazupon.github.io/vue-i18n/guide/sfc.html)
+  - [Hot reloading](https://kazupon.github.io/vue-i18n/guide/hot-reload.html)
+  - [Locale changing](https://kazupon.github.io/vue-i18n/guide/locale.html)
+  - [Lazy loading translations](https://kazupon.github.io/vue-i18n/guide/lazy-loading.html)
+  - [Tooling](https://kazupon.github.io/vue-i18n/guide/tooling.html)
+- [API references](https://kazupon.github.io/vue-i18n/api/)