Apparently the `\zs` token does not match characters if they are already
part of a syntax match. For example in `[^0][^1]` only the zero footnote
is matched. Fix this by using a positive lookbehind that does not have
this limitation.
Additionally, use a negative lookahead for the colon to make the pattern
slightly more readable, since it does not need the end-of-line check.
Julian Prein
372865f9c4
