inspired by: https://www.mstoffel.xyz/posts/ggplot_theme/
for information on themes: https://ggplot2.tidyverse.org/reference/ggtheme.html https://ggplot2.tidyverse.org/reference/theme.html
how to set up a R package: https://pjnewcombe.wordpress.com/2014/05/31/using-rstudio-to-create-and-maintain-an-r-package-on-github/