Use chart "locale" if it is not specified in the adatpter options

[stockiNail]

Fix #71 Answer to comment https://github.com/chartjs/chartjs-adapter-luxon/issues/46#issuecomment-983796300

Missing

• [x] Release new CHART.JS version
• [x] Add test cases using chart locale.
• [x] Add doc in the README

[coveralls]

Pull Request Test Coverage Report for Build 2766431625

• -2 of 2 (0.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-6.7%) to 91.525%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/index.js	0	2	0.0%
<!--	Total:	0	2	0.0%	-->

Totals
Change from base Build 2736928659:	-6.7%
Covered Lines:	31
Relevant Lines:	33

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💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 2766431625

• 0 of 2 (0.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-6.7%) to 91.525%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/index.js	0	2	0.0%
<!--	Total:	0	2	0.0%	-->

Totals
Change from base Build 2736928659:	-6.7%
Covered Lines:	31
Relevant Lines:	33

---

💛 - Coveralls

[LeeLenaleee]

@stockiNail chart.js v3.9 has been released with the necessary changes

[stockiNail]

Thank you @LeeLenaleee. I need to finish a couple of other things for another project and then I'll take care.

[LeeLenaleee]

Yeah no problem, no hurry, just wanted to let you know :)

[stockiNail]

Yeah no problem, no hurry, just wanted to let you know :)

Ready for review! Thank you!

[kurkle]

@stockiNail can you submit a version bump?

[stockiNail]

@stockiNail can you submit a version bump?

Yes, give some minutes

[stockiNail]

@stockiNail can you submit a version bump?

@kurkle done!