Try using HashMap for Dhall.Map

[sjakobi]

Especially with Text keys, HashMap should be faster than Data.Map.

Since we keep a list of the keys in their original order anyway, it shouldn't matter that HashMap is unordered.

[sjakobi]

I see that dhall actually recently switched from a HashMap variant to Map in #612. Did you consider using HashMap instead, @Gabriel439?

[Gabriella439]

@sjakobi: I don't remember why. If HashMap is faster, feel free to switch to it