Add pr_id parameter to support PR comments from workflow_run contexts

[Copilot]

This PR adds support for commenting on PRs from workflow_run triggered workflows, which is essential for handling PRs from external repositories (forks) where the action runs outside the PR context.

Problem

When using workflow_run to handle external PRs (as recommended in the README), the comment feature doesn't work because context.issue.number is not available in the workflow_run context. This prevents users from getting PR comments with test results for external contributions.

Solution

Added a new optional pr_id input parameter that allows explicitly specifying the PR number to comment on:

- name: Publish Test Report
  uses: mikepenz/action-junit-report@v5
  with:
    comment: true
    pr_id: ${{ github.event.workflow_run.pull_requests[0].number }}
    commit: ${{ github.event.workflow_run.head_sha }}
    report_paths: '**/build/test-results/test/TEST-*.xml'

Key Features

• Backward Compatible: Existing workflows continue to work unchanged
• Fallback Logic: Uses pr_id when provided, falls back to context.issue.number
• Input Validation: Handles invalid pr_id values gracefully with helpful warnings
• Robust: Trims whitespace and validates numeric input
• Well Tested: Added comprehensive test suite covering all scenarios including edge cases

Changes Made

• Added pr_id input parameter to action.yml
• Modified attachComment() function to accept and use pr_id when context.issue.number is unavailable
• Updated findPriorComment() to work with the provided issue number
• Added comprehensive test coverage (8 new tests)
• Updated README with parameter documentation and workflow_run example

Testing

All existing tests continue to pass (54 total), plus new tests covering:

• Using pr_id when context.issue.number is unavailable
• Fallback to context.issue.number when pr_id not provided
• Invalid pr_id handling with appropriate warnings
• Whitespace handling in pr_id input
• Comment updating with pr_id parameter

Fixes #1378.

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[github-actions]

	Tests	Passed ☑️	Skipped	Failed ❌️
Example Pytest Report	4 ran	2 passed	0 skipped	2 failed

Test	Result
Example Pytest Report
test_sample.test_which_succeeds	✅ passed
test_sample.test_which_fails	❌ failure
test_sample.test_with_error	❌ failure
test_sample.test_with_flaky_success	✅ passed

• View Example Pytest Report

[github-actions]

	Tests	Passed ☑️	Skipped	Failed ❌️
Example Pytest Report	4 ran	2 passed	0 skipped	2 failed

Test	Result
Example Pytest Report
test_sample.test_which_succeeds	✅ passed
test_sample.test_which_fails	❌ failure
test_sample.test_with_error	❌ failure
test_sample.test_with_flaky_success	✅ passed

• View Example Pytest Report

[github-actions]

	Tests	Passed ☑️	Skipped ⚠️	Failed ❌️
Example Ungrouped Test Report | test_10.xml	3 ran	3 passed	0 skipped	0 failed
Example Ungrouped Test Report | test_11.xml	3 ran	2 passed	0 skipped	1 failed
Example Ungrouped Test Report | test_12.xml	3 ran	2 passed	1 skipped	0 failed

• View Example Ungrouped Test Report | test_10.xml
• View Example Ungrouped Test Report | test_11.xml
• View Example Ungrouped Test Report | test_12.xml

[github-actions]

	Tests	Passed ☑️	Skipped ⚠️	Failed ❌️
Example Ungrouped Test Report | test_10.xml	3 ran	3 passed	0 skipped	0 failed
Example Ungrouped Test Report | test_11.xml	3 ran	2 passed	0 skipped	1 failed
Example Ungrouped Test Report | test_12.xml	3 ran	2 passed	1 skipped	0 failed

• View Example Ungrouped Test Report | test_10.xml
• View Example Ungrouped Test Report | test_11.xml
• View Example Ungrouped Test Report | test_12.xml

[github-actions]

	Tests	Passed ✅	Skipped	Failed
Example Nested JUnit Test Report	3 ran	3 passed	0 skipped	0 failed

Test	Result
Example Nested JUnit Test Report
ABC-0199: XMPP Ping
PingIntegrationTest.pingAsync (Normal)	✅ passed
PingIntegrationTest.pingServer (Normal)	✅ passed
ABC-0045: Multi-User Chat
MultiUserIntegrationTest.mucRoleTestForReceivingModerator (Normal)	✅ passed

[github-actions]

	Tests	Passed ✅	Skipped	Failed
Example Nested JUnit Test Report	3 ran	3 passed	0 skipped	0 failed

Test	Result
Example Nested JUnit Test Report
ABC-0199: XMPP Ping
PingIntegrationTest.pingAsync (Normal)	✅ passed
PingIntegrationTest.pingServer (Normal)	✅ passed
ABC-0045: Multi-User Chat
MultiUserIntegrationTest.mucRoleTestForReceivingModerator (Normal)	✅ passed