⚡improvement(types): typed autocomplete in date and number format options

[Raiondesu]

Replaces Number and Date format options with standard TS Intl types, while also adding guiding TS autocomplete to them.

This change exterminates the confusion of which types to follow, while preserving backwards-compatibility for types and adding optional autocomplete.

This means that upon typing certain formats, the editor will be able to autocomplete some values following MDN guidelines if using typescript:

vuei18n.setDateTimeFormat('en', {
  long: {
    month: '' // Here, TS will suggest 'numerc', '2-digit', 'short', 'long' or 'narrow'
  }
}

while also not restricting anything. So the following will be valid too:

vuei18n.setDateTimeFormat('en', {
  long: {
    month: 'beliberda'
  }
}

essentially making these types backward-compatible with previous versions of vue-i18n.

[codecov-io]

Codecov Report

Merging #485 into dev will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##              dev     #485   +/-   ##
=======================================
  Coverage   96.67%   96.67%           
=======================================
  Files           9        9           
  Lines         662      662           
=======================================
  Hits          640      640           
  Misses         22       22

---

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[codecov-io]

Codecov Report

Merging #485 into dev will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##              dev     #485   +/-   ##
=======================================
  Coverage   96.67%   96.67%           
=======================================
  Files           9        9           
  Lines         662      662           
=======================================
  Hits          640      640           
  Misses         22       22

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ef4b1a6...70594de. Read the comment docs.

[kazupon]

Great work! 🎉
Thanks!