What would be great is a product that is specifically designed to help you deal with a GitHub outage. Oh, GitHub is down? Flip this switch and your developers can somehow keep working.
I and the teams I work with don't come to a stop when GitHub goes down. We can continue to write code, test, commit, review code. You'll have to give more details describing how a GitHub outage prevents developers working.
If you have a development process that halts if GitHub, or any other external service that goes down now and then, rework your process to remove the fragile dependency.
If you have a development process that halts if GitHub, or any other external service that goes down now and then, rework your process to remove the fragile dependency.