Thanks for your interest in the Canasta Project! We always welcome new contributors and we're so glad you're interested in contributing to Canasta.
The best way to be considered for becoming a GSoC contributor is by working on smaller existing items in the backlog, which can be found on our GitHub issues. It's great that you have contributed to extensions in the Wikimedia Foundation; here at Canasta, we are more concerned about quality over quantity. The quality of code contributions and amount of code you write is going to be much more important than the number of commits you make.
Here's a few that we would appreciate your assistance with completing:
We'll not only be looking for code written, but also contributors must demonstrate that their code works and they have tested it out. If there are any ambiguities, it's important for the contributor to ask the questions they need answered so they can complete the job.
Let us know if you have any questions.