Usability of `DecodeHookFunc*` types

[DerGut]

Hi 👋
Thanks for taking over the project!

I've noticed in the past (and today I'm noticing again), that it's not immediately obvious to me how to use the DecodeHookFunc* family of types/ funcs. Both times, I ended up diving into the code to understand how they work from reading the tests and implementations of StringTo{stdLibType}HookFuncs.
The code is very easy to read, so this wasn't exactly a bad experience 😄 But: I'd still expect the GoDoc to contain all the info I need to use them correctly.

IMO they could really use an example and/ or a section in the package overview. Therefore, I suggest to

• add an example for DecodeHookFuncKind, DecodeHookFuncType and DecodeHookFuncValue
• add argument names to the signatures of DecodeHookFuncKind and DecodeHookFuncType (I don't think it's obvious in which order from and to are used, and the third interface{} argument can be cryptic without context)
• perhaps add a section to the top-level package doc string

Would anybody object if I created a PR to do this?

[sagikazarmark]

Hey @DerGut !

A PR would be greatly appreciated! Thanks!