improve documentation

[schmittlauch]

I am using this library for my project, but before getting started with proper usage of it I had to spend several days of experimenting with functions, matching different type signatures to each other, and writing a lot of prototyping code before I figured out how to actually use it. Most function Haddock annotations provide not much more information than the type signature alone. They are a good start but can use much more verbosity, argument annotations and detailed information.

I am relatively new to Haskell, so not being familiar with concepts like parser combinators definitely increased the additional effort for me. But what's missing most dearly is a tutorial/ getting started overview of the different parts of the libraries, their use cases, and some basic example code.

The latter can also be useful for adding tests to asn1-parse and asn1-types.

As I'm just starting to wrap my head around this, I might contribute some documentation at a later point of time.