Smart constructor for Symbol rather than requiring -XOverloadedLists

[ocramz]

It took me a minute to realize coffeeTeaAutomaton only works when OverloadedLists is on. Requiring the extension runs the risk of breaking other code in a module (just happened to me), which is not ideal.

Feature request : Can we have smart constructors for Symbol ? e.g.

symbol :: a -> Label a
symbol = Symbol 

and

symbols :: Foldable t => t a -> Label a
symbols = foldr ((<>) . Symbol) Zero

[snowleopard]

Thanks for the PR! I'm hesitant to change the example in coffeeTeaAutomaton though since it would make it more cluttered. How about extending the corresponding comment, pointing out that the inner lists are overloaded?