Plotly formatting

[eroten]

See _plotly_layout.R

Desired features

• flexible function naming. It would be great to follow the council_{object} syntax, but I've already been using plotly_layout() in several projects. Could we use a simple alias (see https://stackoverflow.com/a/57441165)
• flexible parameter naming - x, x_title both pass to the x-axis title text
• ... to pass additional arguments to plotly::layout(). Show example with legend = list(orientation = "h"), yaxis = list(tickformat = "1%")
• examples and documentation - probably updating the Colors vignette
• font access checks - plotly need access to the various HelveticaNeue woff files. see also separate font load from theme_council()  #47, describe how to install fonts for new users #46