Add West Frisian (fy) support

[damon02]

This adds the West Frisian language spoken in the North of the Netherlands to date-fns.

[damon02]

Hmm no activity here yet, let me explain how and what I based this PR on 😄

For this pull request I worked together with the Provincie Fryslân (where the language is spoken) and had somebody translate and help me put this translation together. I have direct contacts with people at the province through my company, which we use this library for.

I also cross checked this with https://unicode.org/cldr/cldr-aux/charts/32/summary/fy.html#1882 and it seems to match, although that page actually has some words in Dutch and not in Frisian, where the PR has these translated correctly.

I didn't see the PR checklist when creating my PR but when browsing at others it seemed missing so, here you go:

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PR Checklist

To maintain date-fns top quality, please check if PR fulfills the main contributing requirements:

[x] PR follows style guides specified on the guideline: Contributing Guide
[x] Tests for the changes have been added (for bug fixes / features)
[x] Docs have been added / updated (for bug fixes / features)
[ ] Any changes made on the changelog.
[ ] Any changes made on the library version.
[x] Prior to sending pull request FP functions, typings and indices were rebuilt.

What is the new behavior?

With this PR, date-fns will start to support the Frisian (fy) language.

Does this PR introduce a breaking change?

* [ ] Yes
* [x] No

[tan75]

hi @damon02
Apologies for the delay! could you please resolve the conflicts, then run yarn locale-snapshots again (just in case) and push up your code?

[damon02]

I resolved the conflicts by making the PR up to date again with the upstream master branch and re-ran the yarn locale-snapshots command and pushed this.

[tan75]

Thank you for this PR! 🙏