First of all, thank you for showing interest in contributing to Mantine, all your contributions are extremely valuable to the project!
Find task in roadmap that is interesting to you and implement it
We are constantly working on making Mantine better, please share how you use Mantine, what features are missing and what is done good
Fix incomplete or missing docs, bad wording, examples or explanations
Share link to Mantine docs with everyone who can be interested