feat!: deprecate v-t custom directive

[kazupon]

Reason

The advantage of v-t was that it could optimize performance using the vue compiler transform and the pre-translation of vue-i18n-extension.

This feature was supported from Vue 2.
About details see the blog article: https://medium.com/@kazu_pon/performance-optimization-of-vue-i18n-83099eb45c2d

In Vue 3, due to the Composition API, the pre-translation of vue-i18n-extension is now limited only for global scope.

In addition, Vue 3 Virtual DOM optimization has been introduced, and the optimization provided by vue-i18n-extension is no longer very effective. We need to require settings for SSR, the benefits of using v-t have disappeared. And DX of templates using v-t is not good. Custom directives do not work with key completion in editors (e.g. vscode).

For compatibility, v-t mode still works in v11, but will be removed entirely in v12, so v-t will not work after that version.

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commit: f57b836

[BobbieGoede]

LGTM!

[putianyi889]

In addition, Vue 3 Virtual DOM optimization has been introduced, and the optimization provided by vue-i18n-extension is no longer very effective. We need to require settings for SSR, the benefits of using v-t have disappeared.

Can you elaborate? What is the recommended choice then, in terms of performance? Is there an in-depth discussion of this change?