Skip unicode table lookups for ASCII characters in Char.Extra

[dillonkearns]

Short-circuit ASCII characters so common terminators like parens, commas, and braces perform 5 checks instead of 10+ checks. Also moves String.fromChar allocation inside unicodeIsLowerFast/unicodeIsUpperFast to reduce GC work.

Benchmarked at 10-26% faster parsing on real-world Elm files.

[jfmengels]

Amazing! Thank you very much.
And cc @miniBill who made the original version of this IIRC.

[miniBill]

Good catch! I can probably port back some of this to elm-unicode 🤔