Add mailpit and phpMyAdmin to wp-env dev stack

I would like to add the following for a easier developer/tester experience. 

1. I want to be able to spinup **phpMyAdmin** so i have easy access to the testing/development database while using wp-env. 🟢 
2. I want to introduce a mail catcher **Mailpit** that could also be used for testing and debugging emails and email templates. 🟢  

MR: #124 