Ignore docker-compose.override.yml in .gitignore for flexible local setups

[alikhosravidev]

This PR updates .gitignore to exclude docker-compose.override.yml, allowing contributors to use custom Docker configurations without affecting the repository.

Why this change?

Laravel’s core repository includes a docker-compose.yml, but contributors might need additional configurations (e.g., adding a PHP service for running tests in Docker).

docker-compose.override.yml is a built-in mechanism in Docker Compose that lets users extend the default setup without modifying the main file.

By ignoring this file, contributors can define their own overrides without accidentally committing personal configurations.
This makes local development more flexible while keeping the repository clean. 🚀

[taylorotwell]

Thanks for your pull request to Laravel!

Unfortunately, I'm going to delay merging this code for now. To preserve our ability to adequately maintain the framework, we need to be very careful regarding the amount of code we include.

If applicable, please consider releasing your code as a package so that the community can still take advantage of your contributions!