test(@formatjs/intl-datetimeformat): add test for #4270

[longlho]

TL;DR

Add Bosnian (bs) locale support to DateTimeFormat to fix month formatting issues.

What changed?

• Added Bosnian (bs) locale to the test locales in BUILD.bazel
• Added Bosnian locale data (bs.json) with proper month names and formatting rules
• Added a test case that verifies Bosnian month formatting works correctly
• Updated the DateTimeFormat.__addLocaleData call to include the new Bosnian locale

How to test?

Run the new test case that verifies Bosnian month formatting:

// Test for issue #4270: Bosnian month formatting
describe('Bosnian month formatting (issue #4270)', function () {
  it('should format with full datetime options including long month', function () {
    const date = new Date(Date.UTC(2024, 10, 15, 14, 30, 45));
    const fmt = new DateTimeFormat('bs-BA', {
      weekday: 'long',
      year: 'numeric',
      month: 'long',
      day: 'numeric',
      hour: 'numeric',
      minute: 'numeric',
      second: 'numeric',
      timeZone: 'UTC',
    });

    const result = fmt.format(date);
    expect(result).toBe('petak, 15. novembar 2024., 14:30:45');
  });
});

Why make this change?

This change fixes issue #4270 where Bosnian month formatting was not working correctly. Previously, Bosnian dates would display month numbers (like "M11") instead of the proper month names (like "novembar"). By adding the Bosnian locale data with correct month names and formatting rules, dates can now be properly formatted in Bosnian.

[longlho]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• test(@formatjs/intl-datetimeformat): add test for #4270 #5931 👈 (View in Graphite)
• docs: convert rich text formatting to static example, fix #4360 #5930
• build: rm pinned dep #5928
• docs: update polyfills docs #5926
• main

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