Add customizable date and time formats (fixes #25)

[Copilot]

Addresses issue #25 by adding support for customizable date and time formatting in meeting issue titles and agenda times.

Problem

The action currently uses the server's locale for date and time formatting, which produces formats like MM/DD/YYYY dates and 12-hour times. Users wanted the ability to use ISO-8601 YYYY-MM-DD date format and 24-hour time format for better standardization and international compatibility.

Solution

Added two new optional input parameters with backward-compatible defaults:

• DATE_FORMAT: Controls date formatting in issue titles and outputs

  • locale (default): Uses system locale formatting (e.g., 1/15/2025)
  • iso: Uses ISO-8601 format (e.g., 2025-01-15)

• TIME_FORMAT: Controls time formatting in meeting time displays

  • 12 (default): Uses 12-hour format with AM/PM (e.g., 2:30 PM)
  • 24: Uses 24-hour format (e.g., 14:30)

Usage Examples

Default behavior (unchanged):

- uses: target/create-meeting-issue@v1
  with:
    GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

ISO-8601 dates with 24-hour times:

- uses: target/create-meeting-issue@v1
  with:
    GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
    DATE_FORMAT: iso
    TIME_FORMAT: 24

Implementation Details

• Created new formatDate.ts utility module with formatDate(), formatTime(), and formatDateTime() functions
• Updated extractInput.ts to parse the new format parameters with proper defaults
• Modified output.ts to use configurable date formatting for issue titles and GitHub Action outputs
• Updated generateMeetingTimes.ts to use configurable time formatting for timezone displays
• Added comprehensive test coverage for all new functionality (28 tests passing)
• Updated documentation in README.md with parameter descriptions and usage examples

Backward Compatibility

All existing workflows will continue to work without any changes, as the new parameters are optional and default to the current behavior.

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