Shift headings to match size in other courses

Makefile

@@ -59,7 +59,8 @@ $(OUT)/% : $(SRC)/% | $$(@D)
 	cp $< $@
 
 $(OUT)/%.php : $(SRC)/%.md signature.html | $$(@D)
-	pandoc --output $@ --template signature --from markdown --to html $<
+	pandoc --from markdown --to html --template signature --shift-heading-level-by=1 \
+	       --output $@ $<
 
 # Some shell magic to auto-document the main targets. To have a target appear in
 # the output, add a short, one-line comment with a double ## on the same line as