feat: update nuxt docs

[illiyyin]

Hi guys, this is my first open-source contribution pr, let me know what should I do

I tried to use tiptap in my small project using nuxt, after I followed the current instruction. Looks like the code is still using nuxt 2, and I'm using nuxt 3 so I got an error, and then it looks like the code needs to be updated

I don't find the solve on the issue, but I found these issues on the tiptap main repo

• [Documentation]: Update Nuxt example for 3 version tiptap#4965
• docs for Nuxt 3, preferably using composition API with SFC and v-model tiptap#3125

After I tried to debug, my code working.

This pr still needs to be updated tho, since this part here is using embed. I can't find the code on this repo

[vercel]

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