Datepicker: Adding Mongolian localization

[btseee]

As a native Mongolian speaker I'm creating this pull request to add Mongolian language to datepicker.

Баярлалаа (Thank you)

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: btseee / name: Battseren Badral (970d9cf)

[Copilot]

Pull request overview

Adds Mongolian (mn) localization support to the jQuery UI Datepicker, along with coverage to ensure parsing works with Mongolian month names and inclusion in the localization demo.

Changes:

• Added new mn regional configuration file for Datepicker.
• Extended the Datepicker unit tests to load mn and validate parseDate with Mongolian month names.
• Updated the localization demo to load and present Mongolian as a selectable locale.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
ui/i18n/datepicker-mn.js	Introduces Mongolian regional strings and formatting for Datepicker.
tests/unit/datepicker/options.js	Loads the new locale and adds a parseDate assertion for Mongolian month names.
demos/datepicker/localization.html	Includes the new locale module and adds Mongolian to the locale dropdown.

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[fnagel]

Thanks for your contribution!

We need some more reviews of the localization before merging this. Please see here for more info: https://jqueryui.pbworks.com/w/page/139157592/Adding%20translations

This is a follow-up to #1883

[knutsenm]

Regarding the "New language file policy",

be reviewed by at least one thrustworthy native speaking friend of jQuery UI OR

s/thrustworthy/trustworthy/, perhaps? ;-)