Write the example config, including every current config option for every module

We will need to keep this file up to date every time we add a config option or change a default.

I wrote this specifically because Ashton wanted to play around with the server but there was no docs on the config options.
A couple of notes on this block:
- Seeing as all of these are optional modules, I don't think any of them should be uncommented by default. We should stick to only loading the core modules in a default configuration.
- For modules that implement modes and/or commands, we should list what exactly they implement. Therefore it also seems like a good idea to reserve more space between the elements of this list.
- Kinda minor, but maybe we should move this block down so it's right above where the module configuration starts.