Added support for DNS challenges with Simply.com

[manisto]

According to the documentation found at https://www.simply.com/en/docs/api/, a certbot plugin for their API is implemented at https://github.com/JohNan/certbot-dns-simply. This PR adds an entry to dns-plugins.json to enable the use of this plugin. Functionality has been tested with a locally built image, and works with let's encrypt.

[nginxproxymanagerci]

Docker Image for build 1 is available on DockerHub:

nginxproxymanager/nginx-proxy-manager-dev:pr-5119

Note

Ensure you backup your NPM instance before testing this image! Especially if there are database changes.
This is a different docker image namespace than the official image.

Warning

Changes and additions to DNS Providers require verification by at least 2 members of the community!

[manisto]

Is there anything I can do to help speed up the verification process? I am already using the new provider with a locally built image, but it would be nice to be able to use it directly from Docker Hub.