Playground for testing headless modifications

# Description
Testing headless mode during code reviews or its enhancements is tedious since one needs to set up a compilable project under test and manually write all the dependencies, a classpath, etc.

## Proposal
Create a "playground" directory with one or two sample projects and scripts that can execute headless mode "with a single click"- e.g., by running a make command or a bash script **without manual setup of the headless mode parameters**!

# Definition of Done
* [ ] Select one or two projects under test and add them to the repo in a `playground` folder, for instance.
* [ ] Write scripts that successfully execute headless mode on these projects with little or no parameters from the user.
* [ ] Document the headless mode setup so that users with little/no experience with headless mode can set it manually themselves.