Scatter plot does not support X and Plus markers

[alankalb]

Description

When making a scatter plot using 'x', 'X', 'plus' or '+' as the marker shape results in an error as the Scatter plot only supports 'circle', 'square' or 'rect' markers. This is not clear based on documentation or typescript.

Steps to Reproduce

1. Create a scatter plot
2. Add markers to the chart options with 'plus', '+', 'x' or 'X' as the shape

Expected Behavior

Scatter plots can use any shape from the MarkerShapeOptions type

Actual Behavior

Scatter plot crashes when using anything other than 'circle', 'square' or 'rect' as marker shapes

Reproduction Link

https://codepen.io/Alan-Kalbfleisch/pen/KKLorJe