Consider parallelising some Rope operations?

[hawkw]

I think one way we could potentially make some performance gains is parallelising some Rope operations. Since Ropes are immutable, I imagine we could easily use multiple threads for stuff like measuring the O(n) metrics (Lines and Grapheme), etc.

We could also possibly look into using SIMD for stuff like searching a Rope for a given character, or for comparing Ropes.