fix(use-i18n): change props dateFnsLocal to dateFnsLocale

[philibea]

add documentation about dateFnsLocale

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@42fdbfe). Click here to learn what that means.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             master      #137   +/-   ##
==========================================
  Coverage          ?   100.00%           
==========================================
  Files             ?         4           
  Lines             ?       146           
  Branches          ?        17           
==========================================
  Hits              ?       146           
  Misses            ?         0           
  Partials          ?         0           

Impacted Files	Coverage Δ
packages/use-i18n/src/index.js	100.00% <100.00%> (ø)

---

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 42fdbfe...480e880. Read the comment docs.