Make ambiguity errors easier to understand

[jakobnissen]

When you have an ambiguous NFA error, it's bloody hard to figure out what NFA node 41 refers to. Here are two potential solutions:

• When encountering an ambiguity error, print the shortest input sequence that triggers the error.
• Figure out how to attach names to the NFANodes, so the error can say that when in NFA nodes A and B, the ambiguity can occur

[jakobnissen]

Closed in (https://github.com/BioJulia/Automa.jl/pull/64/commits/3784301a140f3c2642932de58abda176b0e7c855)