Add title and footnote to final plots

[SHAESEN2]

We should be able to add footnotes and captions to the final plots. Taking into account that most of the plots might be a result of cowgrid::plot_grid, we could explore some options. One of them could be (although it is not easy to customize):

title <- cowplot::ggdraw() +
cowplot::draw_label(
"KM plot for Time to First Dermatologic Event: Safety population\n",
fontfamily = "sans",
fontface = "bold",
size=10
)

caption <- cowplot::ggdraw() +
cowplot::draw_label(
"\nProgram: tlf_kmplot.Rmd [14OCT2021 10:00]",
fontfamily = "sans",
size=10
)

KM <- cowplot::plot_grid(
title, KM, caption,
ncol = 1,
rel_heights = c(0.1, 0.8,0.1)
)