Allow new github event type i.e `pull_request_target`

[ayushkhandelwal317]

Motivation and Context

This feature will allow users to run spectral-action when github action event type is pull_request_target

Description

Added fall through case for event type pull_request_target

Screenshot(s)/recordings(s)

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• [x] This PR's code follows as closely as possible the coding style/guidelines of this project.
• [ ] I have added error reporting and followed the error reporting guidelines.
• [ ] I have added event tracking and followed the event tracking guidelines.
• [ ] I have updated any relevant documentation accordingly to reflect this PR's changes.
• [ ] I have added automated tests (unit/integration/e2e/other) to cover my changes.
• [ ] All new and existing tests pass locally (excluding flaky CI tests).

[ayushkhandelwal317]

@XVincentX @mnaumanali94 @nulltoken Please take a look at this change.