The very first version:
1. Moves cursort up, down, left, right by grapheme/glyph clusters
2. Breaks lines by grapheme/glyph cluster
3. Just started!
Change-Id: Ib2881794ff33af9e428828f3a9e2d3b54946fa8f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/417476
Commit-Queue: Julia Lavrova <jlavrova@google.com>
Reviewed-by: Mike Reed <reed@google.com>