Add example line and bar charts with negative values to the docs.
Add example line and bar charts with negative values to the docs.

benpickles/peity,wallisnow/peity,wallisnow/peity,dbirchak/peity,FabMeg/tripping-wight,benpickles/peity,dbirchak/peity,benpickles/peity,FabMeg/tripping-wight,dbirchak/peity,wallisnow/peity