Add timeout arg to github repo reader

[rwood-97]

Description

This PR adds a timeout arg to the GithubRepositoryReader to allow users to specify a timeout when making requests. Fixes #846

Type of Change

Please delete options that are not relevant.

• [x] Bug fix / Smaller change

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• [ ] Added new unit/integration tests
• [x] I stared at the code and made sure it makes sense

Suggested Checklist:

• [x] I have performed a self-review of my own code
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] I ran make format; make lint to appease the lint gods

[anoopshrma]

Thank you for the contribution!

[nerdai]

Thanks for the fix @rwood-97 !