approved_layers: Approved Geoms, Stats and Positions
Description
ggtern is a specialist extension to ggplot2 for rendering ternary diagrams, as such, many stats and
geoms which come packaged with ggplot2 are either not relevant or will not work, as such,
ggtern regulates during the plot construction process, which geoms and stats are able to be applied
when using the coord_tern coordinate system. Attempting to apply non-approved geometries or stats
(ie geometries / stats not in the below list), will result in the respective layers being stripped from the final plot.