Add PR (Pull Request) Support to GitHub App for Stories

Enhance GitHub integration to automatically create and attach test runs to pull requests (PRs) when detected.

• If Pull Request Testing is enabled for a repository, TestQuality should automatically create a PR check/run when an associated PR is detected for a story.
• In GitHub, this would link the PR to the corresponding issue.
• For Jira, if a Jira key (e.g., [TQ-99]) is present in the PR name, the test run should be associated with that issue.

This feature aims to streamline the testing workflow by automating test execution for PRs, ensuring better traceability and faster feedback loops.