v2.8.1

UnicodePlots v2.8.1

Diff since v2.8.0

Merged pull requests:

• Reduce allocs (#223) (@t-bltg)
• Interpolate color when using lines on surfaceplot (#224) (@t-bltg)
• Update doc example (#225) (@t-bltg)
• Support vector of colors (barplot, boxplot) (#227) (@t-bltg)
• Bump NaNMath compat (#228) (@t-bltg)