Comparison/benchmarks with rivo/uniseg

[ossenthusiast]

https://github.com/rivo/uniseg

[kolkov]

Done in v0.2.0.

Three-way benchmarks (uniwidth vs go-runewidth vs rivo/uniseg) now run automatically on every PR. See the comparison table from the first run:

#2 (comment)

[ossenthusiast]

Thank you for your hard work!