Add tag_facet function?

[nonsciencemark]

Would it be possible to swipe the tag_facet function from egg and incorporate it such that it plays nicely with facet_nested?

I think the only thing that's needed is to take the current version:

tag_facet <- function(p, open = "(", close = ")", tag_pool = letters, x = -Inf, y = Inf, 
                      hjust = -0.5, vjust = 1.5, fontface = 2, family = "", ...) {
    gb <- ggplot_build(p)
    lay <- gb$layout$layout
    tags <- cbind(lay, label = paste0(open, tag_pool[lay$PANEL], close), x = x, y = y)
    p + geom_text(
        data = tags, aes_string(x = "x", y = "y", label = "label"), ..., hjust = hjust, vjust = vjust,
            fontface = fontface, family = family, inherit.aes = FALSE) +
        theme(strip.text = element_blank(), strip.background = element_blank())
}

and remove that last theme line and then we get beautiful, automatically-labelled facets. I would consider this to be h4x and egg hasn't been updated in 4 years