Revisons of time series standards

[mpadge]

Points raised by @rkillick in her review of the brolgar package by @njtierney as "not covered but should be":

• Visualizations being appropriate; this should be in the general standards section. Within the review the only bit currently covered was that the time axes should be labelled appropriately and should usually be on the x-axis. This isn't enough.

That suggests addressing the following point

• Expand standards for visualizations produced by time series software