add link to comments in Makefile

Makefile

@@ -21,6 +21,7 @@ deploy:
 	@$(SPHINXBUILD) -M html "$(SOURCEDIR)" "$(BUILDDIR)" -nW
 	#  -n   Run in nit-picky mode. Currently, this generates warnings for all missing references.
 	#  -W   Turn warnings into errors that stop the build.
+	# for more details about the options see https://www.sphinx-doc.org/en/1.8/man/sphinx-build.html#options
 
 # Catch-all target: route all unknown targets to Sphinx using the new
 # "make mode" option.  $(O) is meant as a shortcut for $(SPHINXOPTS).