Add html-nohighlight make target

This generates the html without syntax highlighting to speed things up for
development work.

Makefile

@@ -3,6 +3,9 @@
 html:
 	perl6 htmlify.pl
 
+html-nohighlight:
+	perl6 htmlify.pl --no-highlight
+
 run-all:
 	perl6 bin/run-examples.pl
 
@@ -16,7 +19,8 @@ help:
 	@echo "Usage: make [html|test]"
 	@echo ""
 	@echo "Options:"
-	@echo "   html:         generate the HTML documentation"
-	@echo "   run-all:      run all examples"
-	@echo "   test:         test the supporting software"
-	@echo "   web-server:   display HTML on localhost:3000"
+	@echo "   html:              generate the HTML documentation"
+	@echo "   html-nohighlight:  generate HTML without syntax highlighting"
+	@echo "   run-all:           run all examples"
+	@echo "   test:              test the supporting software"
+	@echo "   web-server:        display HTML on localhost:3000"