fill and fontface otions for geom_gene_label about gggenomes HOT 4 CLOSED

g0 <- tibble(seq_id="a", start=10, end=500, gene="foo")
gggenomes(g0) +
  geom_gene(aes(fill=gene)) +
  geom_gene_label(aes(label=gene, color=gene), fontface="italic", show.legend=FALSE)

# thought this would work with `parse=T` but got no character for psi at all
g0 <- tibble(
  seq_id="a", start=c(10, 600), end=c(500, 1000),
  # this seems to work just fine
  gene=c("foo", "ψ"),
  # thought this would work with `parse=T` 
  # but got no character for psi at all
  gene_parse=c("foo", "psi"),
  # unicode seems to work as well
  gene_unicode=gsub("ψ", "\u03C8", gene)
)

gggenomes(g0) +
  geom_gene(aes(fill=gene)) +
  # psi and italic
  geom_gene_label(aes(label=gene, color=gene), 
                  fontface="italic", show.legend=F, nudge_x=-100) +
  # no psi, and not italic
  geom_gene_label(aes(label=gene_parse, color=gene), 
                  fontface="italic", show.legend=F, parse=T) +
  # psi and italic
  geom_gene_label(aes(label=gene_unicode, color=gene),
                  fontface="italic", show.legend=F, nudge_x=100)