How much of the genome is in genes?

If you've followed so far you should have:

• a table genes of genes (with some statistics from the 'canonical' transcript).
• a table regions of regions including chromosomes or other contigs, describing the assembly.
• and you should have (or know how to get) other things like a dataframe of transcripts and an exons.

Let's use this to try to figure out how much of the genome is actually covered by genes.