Convert scatter plot to VictoryCharts

[jaronheard]

We are moving from Recharts to VictoryCharts. See also issue #44.

The existing ScatterPlot component needs to be converted to the VictoryCharts equivalent: https://formidable.com/open-source/victory/docs/victory-bar/

The purpose of having our components wrap VictoryCharts is to prescribe stylistic choices, such as colors, line weight, spacing, etc.

Todo:

• [x] Add VictoryCharts as a dependency
• [x] Rewrite the ScatterPlot component
• [x] Add unit tests
• [x] Update the ScatterPlot story

The basic scatterplot should look like this, and have all of the components shown in this chart.

Generally, I'm expecting that the color and font styling will be inherited from a common VictoryTheme, so don't worry about the color and font for this issue.

In addition to what is shown, Scatterplot should have the following features:

• [x] Accessibility description
• [x] Responsive

[jaronheard]

I've updated the design in the original issue. The tooltip shown is addressed in #65.

[jaronheard]

130 addresses