Sepia and Night themes don't specify anchor color for <code>

[softmoth]

It is hard to spot links in the guide when using the Sepia or Night color scheme, because when they are in <code> text they look just like normal text.

For example, on https://guide.elm-lang.org/interop/flags.html#verifying-flags, there is one Json.Decode.Value link (in the unordered list). It's visibly a link in the White theme, but in the Sepia and Night themes it looks like normal text.