Documentation to support non-DotNet users

**Is your feature request related to a problem? Please describe.**

Several years ago I used roundhouse for a project at a different company. Now I have an opportunity to use grate at my new company and I'm running into roadblocks.

Back then it was "easy" because I could mostly copy the connection strings from my app and things would just work. Now I'm working in NodeJS and my connection strings have a different structure and figuring out the right syntax is a bit a of problem. For example, I built a demo to show off grate and I spent _most_ of my time trying to figure out how to write the connection string so it would work in docker compose with pgsql. I had to run down the different packages I thought you were using, and then _eventually_ guessed right after looking at the tests (yes I should have started there). All in all, it was a pain.

**Describe the solution you'd like**
It would be helpful if the documentation contained clear instructions on the connection strings for the various supported databases (minimally links to the definitive docs). It would also be very helpful if the docker examples were extended to include each of the supported databases (or just the ones I use) especially if instead of using a single env var for the connection strings, you all the variables bits (host, ports, admindb ...) were put into individual env vars. This would go a long way to letting people who like the simplicity of grate, but don't want to deep dive into C# and .Net just yet.