Make public-facing type aliases public

[Grimeh]

Hey there,

First time using fuzzy-matcher and I noticed that ScoreType isn't pub. This is a bit of a pain if you want to store the scores anywhere, as it forces the user to use the explicit i64 type. This is an ergonomics, usability, and readability issue.

Enabling or disabling the "compact" feature will cause compilation errors if the user is storing score results anywhere. It also makes upgrading the crate version riskier for users, as the backing type of ScoreType or IndexType can change.

Afaik there's no downside to making these types pub, please correct me if I'm wrong.

Builds OK. Was not able to run tests, could not compile termion since I am on Windows.