- Add GROUP_BY, SORT_BY, and SORT_ORDER environment variables
- Implement sort_issues() to sort by time_to_close, time_to_first_response, etc.
- Implement group_issues() to group by author or assignee
- Add comprehensive unit tests for sorting and grouping functionality
- Update README.md with documentation for new configuration options

Co-authored-by: zkoppert <6935431+zkoppert@users.noreply.github.com>

Signed-off-by: Zack Koppert <zkoppert@github.com>

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Signed-off-by: Zack Koppert <zkoppert@github.com>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Fix EnvVars.__repr__ with proper comma separators and closing paren
- Add descending sort order assertion to test_sort_with_none_values

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…uping-sorting-options

feat: add grouping and sorting options for shipped work report