[TRIGGER] Discord Bot message triggers

**Discord Message**
Whilst Pipedream can trigger actions on Discord, there is no simple way for Discord users to communicate with the Discord bot, triggering Pipedream workflows.

Triggers which would assist with this include:
- Listening for direct messages from users to the bot
- and / or listening in a specified channel for a specific command string (eg: !runprocess) [Slash commands?](https://discord.com/developers/docs/interactions/application-commands#slash-commands)

**API**
https://discord.com/developers/docs/reference
[Webhooks](https://discord.com/developers/docs/interactions/receiving-and-responding#receiving-an-interaction) seem to be an option instead of gateway which may be an easier option.