I'm just learning about quantum computer but some of it has been available for people to research & practice so I'd like to study it myself. The only kind of quantum computing I found so far is IBM cloud service and Q# quantum simulator but the sources and examples are limited, and I only found a bunch of display emoji & a card-guessing mini-game in quantum programming. Are there any main sources like GitHub but for quantum computing programming?
Are you looking for algorithms to look through, or programs for an actual quantum computer?
If the former the IBM Q Experience user guide has good explanations of some of them, and other questions you can find on this Stack Exchange can get you to more algorithms.
If you are looking for programs to be run on a quantum computer like IBM's cloud offerings, I'm not sure if there is a github specific to is, but looking into the Qiskit github would be a good place to start!
If you want to start studying Q# by writing small quantum computing programs, there is Quantum Katas repo, it has less code and the code is simpler but it aims specifically to teach the basics.
There is no GitHub like service dedicated to quantum programming. It is all on standard GitHub.
For QISKit, the tutorial has quite a large number of examples. Beyond the simple 'Hello World' example, most resources are found in the reference folder.
You'll also find things scattered around on the pages of single GitHub users. To find these, you could try looking at who has forked the SDKs or participated in quantum hackathons.