Improvements to the post processor

[mariusbarth]

Is your feature request related to a problem? Please describe. I think it is tedious to always write Figure\ \@ref(fig:chunk-name), i.e. I forget to write the non-breaking space, frequently.

Describe the solution you'd like maybe we should explore the possibility to run a gsub() in the post processor.

Describe alternatives you've considered maybe this is something that would be interesting for the bookdown authors and should be considered there.

Additional context Add any other context or screenshots about the feature request here.