feat: nuxt 3 support

[nozomuikuta]

This draft PR aims to take over #103 and resolves #106.

At first, for the next major release, I triaged all the open issues as below (except Renovate Dependency Dashboard (#99)).

My implementation may include some breaking changes in API, as done in #103, in a way that I believe is good and beneficial enough for users. I would like to discuss with authors and community while developing this PR.

This PR doesn't aim to add Docus-powered documentation, which is handled in #103, so that we can keep this PR's "done of definition" manageable.

This PR message will be modified as needed.

TODOs

• [x] Scaffold by Nuxt module starter
• [x] Restore LICENSE
• [x] Restore CHANGELOG.md
• [ ] Rewrite README.md
• [ ] Restore/Modify Renovate configuration
• [ ] Restore/Modify Commitlint configuration
• [ ] Restore/Modify Husky configuration
• [ ] Restore/Modify testing
• [ ] Restore/Modify GitHub Actions
• [ ] Implement module with new features (✨), breaking changes (⚠️), and bug fixes (🔧)
  • [ ] Feed file generation (blocked by https://github.com/nuxt/framework/issues/4698)
    • [ ] Atom file generation
    • [ ] JSON file generation
    • [ ] RSS file generation
  • [ ] middleware for feed SSR
  • [ ] cache time for each feed (async-cache package is deprecated, can nitro's unstorage layer be an alternative?)
  • [x] create function for each feed
  • [x] data passed to create function for each feed
  • [x] ✨ common create function for all feeds
  • [x] ✨ common data passed to create function for all feeds
  • [x] ✨ #9
  • [ ] ✨ #70 (need spec)
  • [ ] ✨ #89 (need spec/research)
  • [ ] ✨ #95 (blocked by https://github.com/jpmonette/feed/issues/98)
  • [x] ⚠️ feed sources factory function (sources option can be a function instead of factory option)
  • [ ] ⚠️ data passed to feed sources factory function (not sure about use case, can be deprecated (?))
  • [x] 🔧 #63 (fixed by breaking change on factory option)
  • [ ] 🔧 #102 (need research)

Out of Scope

• Implementation
  • #15 (looks stale)
  • #100 (looks stale)
• Documentation
  • GraphQL/Apollo example
    • #5
    • #11
  • #94
  • #62