This commit moved ExecuteWebhookData from package api to package webhook
inside package api. This change required splitting the multipart
abstractions away from package api, so they are now inside package
sendpart in utils.
This commit will break code that uploads anything, as the type name is
now sendpart.File from api.SendMessageFile. The behavior should be the
same as before.
* Webhook: Add support for message edit and delete
* Webhook: remove global functions
* Webhook: move package Webhook into api/
* Webhook: Moved (unused in API) data struct to package webhook
Co-authored-by: diamondburned <datutbrus@gmail.com>