Use optional peerDependency to ensure latest @intlify/vue-i18n-loader is used with Vue I18n v9

[WIStudent]

Clear and concise description of the problem

According to the README, the latest @intlify/vue-i18n-loader requires Vue I18n v9:

This package of @intlify/bundle-tools is for Vue I18n v9 or later!
The version for Vue I18n v8.x is now in @intlify/vue-i18n-loader v1.x!

This should be enforced in the package.json.

Suggested solution

Use optional peerDependency to require v9 if vue-i18n is installed.

{
  "peerDependencies": {
    "vue-i18n": "^9.0.0"
  },
  "peerDependenciesMeta": {
    "vue-i18n": {
      "optional": true
    }
  }
}

Alternative

No response

Additional context

No response

Validations

• Read the Contributing Guidelines.
• Read the README
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.

[pmrotule]

I ran into the same issue: I had to dig deep to find that the latest version of @intlify/vue-i18n-loader was for Vue 3. I would personally also add Vue 3 as peer dependency to make it extra clear. Moreover, I wouldn't add "optional": true since it is not optional: you have to use vue-i18n v9 or later otherwise it won't work.

[kazupon]

I've fixed and released out!
Please check it!
Thanks!