Extend makefile to simplify debugging

Signed-off-by: David A. Wheeler <dwheeler@dwheeler.com>

makefile

@@ -13,12 +13,29 @@ toc.md: secure_software_development_fundamentals.md tocignore
 linklist.md: toc.md make_linklist
 	./make_linklist < toc.md > linklist.md
 
+# Generate user-viewable versions.
+# NOTE: This is intended to help develop and debug the course.
+# If you simply want to *learn* the material, this is a terrible way to do it.
+# Instead, take the free course, it's available here:
+# https://training.linuxfoundation.org/training/developing-secure-software-lfd121/
+
+PANDOC = pandoc
+PANDOCFLAGS = -f gfm-tex_math_dollars
+
 # This requires wkhtmltopdf because it goes via HTML
 # https://plaintextproject.online/articles/2022/04/06/pdf.html
 # https://stackoverflow.com/questions/38455078/specifying-papersize-for-md-to-pdf-conversion
 # We don't include this because it shows the title twice:
 # --metadata title="Secure Software Development Fundamentals"
 book.pdf: secure_software_development_fundamentals.md
-	pandoc -f gfm --pdf-engine=wkhtmltopdf \
+	$(PANDOC) $(PANDOCFLAGS) --pdf-engine=wkhtmltopdf \
 		--css=print.css -V geometry:a4paper -o book.pdf \
 	  secure_software_development_fundamentals.md
+
+secure_software_development_fundamentals.html: \
+  secure_software_development_fundamentals.md
+	$(PANDOC) $(PANDOCFLAGS) -t html $< > $@
+
+html: secure_software_development_fundamentals.html
+
+.PHONY: all lint html