add handout targets

Makefile

@@ -7,10 +7,14 @@ help: ## Print the help message
 # Search should not include slides separated by '***', as those are for mdp, not pandoc.
 markdown != find slides/ -maxdepth 2 -type f -name "*.md" -exec grep -LF '***' '{}' ';'
 pdfs = $(patsubst %.md, %.pdf, $(markdown))
+handouts = $(patsubst %.md, %_handout.pdf, $(markdown))
 
 $(pdfs): %.pdf: %.md
 	pandoc -t beamer -V theme:Warsaw -i $< -o $@
 
+$(handouts): %_handout.pdf: %.md
+	pandoc -t beamer -V handout -V theme:Warsaw -i $< -o $@
+
 .PHONY: pdfs
 pdfs: $(pdfs) ## Generate all pdfs (try `make -j pdfs`)