Support Plunk for email providers

[Martinsos]

trafficstars

Discussed in https://github.com/wasp-lang/wasp/discussions/2215

^{Originally posted by Reikon95 July 31, 2024} I use plunk in other projects and it's great - simple API and easy pricing plan to understand. Would be great if it was supported as one of the providers

https://www.useplunk.com/