The slack API is documented well, but can be confusing as there are multiple APIs, API Tokens, Permissions to deal with. Having our own documentation for the APIs, such as @slack/web-api and @slack/events-api, PGSQL and the folder structure that we use, would make it easier for new contributors to join in on the fun.
Anybody who might want to take this up can hit us up on #watermelone-help on the pesos slack channel and we can help you out.