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.

status.json

@@ -2,6 +2,6 @@
     "no_comment" : "mandatory comment: because comments were removed from the original JSON spec",
     "IOCCC_status_version" : "1.0 2024-03-09",
     "contest_status" : "closed",
-    "news_update" : "2024-03-18T08:08:33+00:00",
-    "status_update" : "2024-03-18T08:08:34+00:00"
+    "news_update" : "2024-03-20T07:14:44+00:00",
+    "status_update" : "2024-03-20T07:19:04+00:00"
 }