Allow to configure the Plunk API connection parameters

[bn3t]

• Component or Package Name: CLI preview
• Component or Package Version: latest

Feature Use Case

Currently in the preview the send via Plunk is hardcoded to use Plunk (the real one). I think it would be nice to configure a self hosted one like I have.

Feature Proposal

Have the API url and API key configurable via command line or environment.

[shellscape]

I'd be willing to take a look at a PR that added support for those to the config file. I think the CLI would get a bit noisy.

[bn3t]

Yeah sure, but I will not use your plunk account to test my emails. In the meanwhile, I have added the ability to send test emails inside my application. So maybe add an option to just disable this feature inside the jsx-email preview.
Anyways, thanks for the great project, much easier to use than react-email.