Clean up and document project files (#4560)

docs/mkdocs/Makefile

@@ -1,39 +1,35 @@
 # serve the site locally
-serve: prepare_files style_check
+serve: style_check
 	venv/bin/mkdocs serve
 
-serve_dirty: prepare_files style_check
+serve_dirty: style_check
 	venv/bin/mkdocs serve --dirtyreload
 
-build: prepare_files style_check
+# This target is used in the CI (ci_test_build_documentation).
+# This target is used by the docset Makefile.
+build: style_check
 	venv/bin/mkdocs build
 
-# create files that are not versioned inside the mkdocs folder (images, examples)
-prepare_files: clean
-	mkdir docs/examples
-	cp -r ../json.gif docs/images
-	cp -r ../examples/*.cpp ../examples/*.output docs/examples
-
 style_check:
-	@cd docs ; python3 ../scripts/check_structure.py
+	@cd docs ; ../venv/bin/python3 ../scripts/check_structure.py
 
-# clean subfolders
-clean:
-	rm -fr docs/images/json.gif docs/examples
+# check the links in the documentation
+link_check:
+	ENABLED_HTMLPROOFER=true venv/bin/mkdocs build
 
 # publish site to GitHub pages (not working in GitHub Actions; need special action)
-publish: prepare_files
+publish:
 	venv/bin/mkdocs gh-deploy --clean --force
 
 # install a Python virtual environment
+# This target is used by the docset Makefile.
 install_venv: requirements.txt
 	python3 -mvenv venv
 	venv/bin/pip install --upgrade pip
-	venv/bin/pip install wheel
 	venv/bin/pip install -r requirements.txt
 
 # uninstall the virtual environment
-uninstall_venv: clean
+uninstall_venv:
 	rm -fr venv
 
 update_requirements: