Create an entrypoint for the docker image to make bootstrapping easier

[yangm97]

As outlined by #196 the process to get construct up and running using the container images is somewhat under-documented and convoluted.

We can borrow some inspiration from the entrypoint.sh files in database container images like postgres, since they automatically perform first time setup with sane defaults (where possible).

Some requirements that I can foresee are:

• ensure user provided the domain for bootstrapping
• default listener needs to be non-tls, as most container users will have some ingress infrastructure in place already
• Until Reverse proxy support #189 is closed, default to maximum connections per client (same reason as above)