Credentials - in my experience they just aren't a thing in software development. Apart from juniors just starting out I've never once seen a CV or a job application that mentioned any kind of programming credentials or certifications (if I understand you're meaning of "credentials" correctly?). For getting into a new area of development some ways to prove yourself are:

1. Contribute to open source codebases

2. Work on side projects

3. Convince your existing company to use a new technology so you can work on it in your day job.

Maybe others? I can't think of anything else right now..

Github profiles can be a bit hit or miss - I think probably most people don't really look at them. However if you have made meaningful contributions to open source codebases on github then you can link to those in your CV, or mention it on your covering letter or just mention it in the interview.