This package was merged into https://github.com/RocketChat/Rocket.Chat.Apps-engine, please refer to it for issues and contributions. You can find the code we had here at https://github.com/RocketChat/Rocket.Chat.Apps-engine/tree/master/src/definition.
The npm package @rocket.chat/apps-ts-definition will be updated for some time but it was deprecated and we enforce the usage of @rocket.chat/apps-engine.