feat(locale): Mongolian locale

[javkhaanj7]

PR Checklist

Before creating new PR, please take a look at checklist below to make sure that you've done everything that needs to be done before we can merge it.

• read and followed the CONTRIBUTING.md guide.
• built and tested the changes locally.
• added/updated tests.
• added/updated API documentation.
• added/updated demos.

[codecov]

Codecov Report

Merging #4161 into development will decrease coverage by <.01%.
The diff coverage is 85%.

@@               Coverage Diff               @@
##           development    #4161      +/-   ##
===============================================
- Coverage        72.24%   72.23%   -0.01%     
===============================================
  Files              256      254       -2     
  Lines             8293     8258      -35     
  Branches          1589     1575      -14     
===============================================
- Hits              5991     5965      -26     
+ Misses            1873     1867       -6     
+ Partials           429      426       -3

Impacted Files	Coverage Δ
src/locale.ts	100% <100%> (ø)	⬆️
src/chronos/i18n/mn.ts	84.21% <84.21%> (ø)
src/chronos/i18n/it.ts	71.42% <0%> (-28.58%)	⬇️
src/chronos/i18n/uk.ts	78.04% <0%> (-2.44%)	⬇️
demo/src/app/docs/api-docs/analytics/analytics.ts	36.36% <0%> (-1.74%)	⬇️
...hemes/bs/bs-daterangepicker-container.component.ts	30.76% <0%> (ø)	⬆️
demo/src/app/app.component.ts	34.28% <0%> (ø)	⬆️
...ker/themes/bs/bs-datepicker-container.component.ts	38.7% <0%> (ø)	⬆️
src/dropdown/bs-dropdown.directive.ts	74.01% <0%> (ø)	⬆️
src/chronos/i18n/pl.ts	72.22% <0%> (ø)	⬆️
... and 9 more

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[valorkin]

thanks for your PR!
sorry for a delay, I was organizing https://ngtalks.io

[javkhaanj7]

Thank you. Good luck on your NgTalks conference.

[valorkin]

@javkhaanj7 thanks, I will be merging more PRs this and next week

[valorkin]

new version should be tested and published next Friday