Fix i18n documentation
Fix i18n documentation

There is a missing `extends` for the Localized Message Bundle so the `@Override` doesn't make much sense right now.

There should be additional information somewhere also on setting the Locale, which I had to find in the unit tests:
```
templateInstance
                    .setAttribute(MessageBundles.ATTRIBUTE_LOCALE, Locale.forLanguageTag(locale)
```
quarkusio/quarkus,quarkusio/quarkus,quarkusio/quarkus,quarkusio/quarkus,quarkusio/quarkus