Plot.tip should support textOverflow

[Fil]

Currently, textOverflow is ignored in tips that use key/value pairs formatting. (It's appied only in the case where the tip is specified with the title channel).

Plot.tip(
  [
    {
      what: "A long long long long long long long long long long long long way home",
      textOverflow: "ellipsis-middle"
    }
  ],
  { x: "what" }
).plot()