improve Copyright and CC

The inc/footer.default.html now has a common Copyright and CC BY-SA
4.0 License section for all generated HTML files.

All markdown files have a similar Copyright and CC
at the bottom in the form of an HTML comment.

2018/ferguson/rpm.md

@@ -40,3 +40,18 @@ further. Nevertheless more information on my entry can be found at
 
 [errata page]: https://ioccc.xexyl.net/2018/weasel/errata
 [https://ioccc.xexyl.net/2018/weasel]: https://ioccc.xexyl.net/2018/weasel
+
+
+<!--
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