First off, thank you for considering contributing to Doccano. It’s people like you that make open source thrive, and make Doccano a great tool.
Doccano is under continuous development, in both the original project and this fork made by Gong.io. As a mature company that works at scale, we at Gong.io developed many features on top of the original project, to support scalability, better maintanence and faster annotation. We continue active development according to our needs and issues and requests arising from the open-source community at this fork.
If you have requests for features, please file an issue describing your request. Also, if you want to see work towards a specific feature, feel free to contribute by working towards it. The standard procedure is to fork the repository, add a feature, fix a bug, then file a pull request that your changes are to be merged into the main repository and included in the next release.
Here are some tips that might help - How to contribute to the project