fix(nuxt): wrap ssr plugin in defineNuxtPlugin

[dan-online]

Description

When using the nuxt package, the console outputs the warning:

[warn] [nuxt] You are using a plugin that has not been wrapped in `defineNuxtPlugin`. It is advised to wrap your plugins as in the future this may enable enhancements: () => { }

This pull request simply wraps the ssr-plugin file export with defineNuxtPlugin

Additional context

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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• Read the Contributing Guidelines.
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• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
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• Ideally, include relevant tests that fail without this PR but pass with it.