Support ws subscriptions for nuxt and h3 (with doc)

[Dodobibi]

Description

Add the support of ws subscriptions for nuxt and h3

Performance impact

unknown (not)

Security impact

unknown (not)

Checklist

• My code matches the project's code style and yarn lint:fix passes.
• I've added tests for the new feature, and yarn test passes.
• I have detailed the new feature in the relevant documentation.
• I have added this feature to 'Pending' in the RELEASE_NOTES.md file (if one exists).
• If this is a breaking change I've explained why.

[changeset-bot]

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Latest commit: 828ed9d

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[benjie]

Awesome; so happy to see this being updated to a more stable implementation! Some early comments; my main question is around the path to the websocket handler, and why serv can't handle that internally rather than having the user write additional code. If there's a good reason behind this it's fine, I just want to know what that reason is (as an outsider unfamiliar with H3/Nuxt).

[benjie]

Looking good! I've done some refactoring, and have some questions