Feature Request: Dedicated Key for Graceful Exit in --watch Mode

Currently, when gotestsum is running in --watch mode, the only way to exit the process is via a Ctrl+C interruption. While Ctrl+C is a standard way to interrupt a process, it results in a non-zero exit code, which doesn't offer a "graceful" way to exit the program.

I propose adding a key like q or e that allows users to perform a graceful exit from the --watch mode. This would provide a cleaner and more intentional way to stop the process.

If that makes sense for the project, I'm interested in contributing to this feature. I'm a beginner in Go and would appreciate any advice or guidance on implementing this feature.