Add a way to get Sphinx' version (#1876)

* Add a way to get Sphinx' version

This can bes tested [here](www.sphinx-doc.org/en/stable/) and [here](https://clang.llvm.org/docs/AddressSanitizer.html)

* Walk around the stupid CI :>

src/apps.json

@@ -8127,6 +8127,7 @@
 				"4"
 			],
 			"env": "^DOCUMENTATION_OPTIONS$",
+			"html": "Created using <a href=\"https?://sphinx-doc\\.org/\">Sphinx</a> ([.\\d+])+\\.\\;version:\\1",
 			"icon": "Sphinx.png",
 			"implies": "Python",
 			"website": "http://sphinx.pocoo.org"