Find a way to use the runDebugEmail.sh script with Docker locally

[ssciolla]

Currently, there is no easy way to set up the mock email server (a process defined in runDebugEmail.sh) while also using Docker Desktop to run the application. You can set the SEND_EMAIL environment variable from the command line when using docker run, but we need a way to set up the mock email server as a background process that only runs for as long as the main program is running. There is likely a way to do this by modifying start.sh.