Interaction error responses

[paperdave]

If an interaction handler throws and the interaction wasn't responded to, we could consider calling .showMessage with a formatted error.

Two forms of errors should be accepted, one being a custom error class like InteractionError, which contains CreateMessageData and can be passed directly as the response, with normal errors having a preset formatter.

This behavior should be configurable within the config, so we might be depending on #9. Config should follow this schema:

• interactionErrors.enable if this behavior is enabled or not
• interactionErrors.formatter a function to format an Error to a CreateMessageData
• interactionErrors.ephemeral (true default), specifies what the ephemeral flag is default to, if the formatter doesn't specify this flag.
• interactionErrors: false disable entirely
• interactionErrors: true enable with default settings

[paperdave]

when InteractionError is written, the default formatter should be a static method on it, meaning the default config entry is just formatter: InteractionError.defaultFormatter