Dialogflow - Conversational UX Platform. (ex API.ai)
Bootstrap 4 Cheat Sheet - An interactive Bootstrap 4 cheat sheet
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Bootstrap Zero - Open-source, free Bootstrap templates collection.
Botkit - Botkit is an open source developer tool for building chat bots, apps and custom integrations for major messaging platforms.
HackerThemes - Bootstrap 4 themes and tools for web developers