Canvas background colour chartjs plugin

Create an option to colour the canvas background. The function produces a list that will become an object within the plugins array x$plugins[plugin]. The id will become the plugin name, and this fuction takes in a color parameter, thus x$options$plugins$canvasBackgroundColor$color <- "some colour". This is accessed using cjs_theme(chart.backgroundColor = ...)

canvasBackgroundColor()

Value

a list