Make error messages prettier #9
Description
Really doing this would probably require handing a custom exception to the end user so that they can format it as they want, but with the amount of information we have at compile time it shouldn't be too tricky to get basic Megaparsec-style errors at least
the goal should be:
- useful, clear, compile time messages for developers (eg for invalid config specs)
- idiot-proof runtime error messages for users (e.g for missing properties). this is the most important as it's the most work for a developer to write - so we want to automate this as much as possible