feat: avoid displaying the key until loading

[rozsazoltan]

If the page is not loaded based on SSR, then when the language file loading takes even slightly longer than the rest of the frontend, the key briefly appears for a very short time. This creates a sensation of "vibration". It would be much better if the wTrans (and other dependent functions) function returned nothing until the loading is complete.

I've made a video (not the most professional, but it illustrates the difference), playing back the loading process at 0.1x speed.

https://github.com/xiCO2k/laravel-vue-i18n/assets/67325669/cab5a542-2e26-4707-a1c7-429d1ff533f6