Move 2014/vik bug notice from years to README.md

As the years.html file will be generated with a tool (yet to be written)
having the bug notice will (greatly)? complicate the generation. Thus
the bug notice (which I discovered when working on 2020/ferguson2) was
moved to 2014/vik/README.md.

But why? Because it is a good idea, I think, to note that although
mostly correct, there is a minor problem with it. I don't have a fix for
it but whether I ever look at that I do not know.

I also made a minor change in 2020/ferguson2/README.md: changed a full
stop to an exclamation mark as it seemed better.

2014/vik/README.md

@@ -38,6 +38,10 @@ might speak to your coding style? If not, then perhaps:
 
 might help? :-)
 
+NOTE: In 2020 Cody Boone Ferguson found a minor bug when working on his [Enigma
+machine entry](../../2020/ferguson2); see his
+[README.md](../../2020/ferguson2/README.md) for details (search for `vik`).
+
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