Error message could suggest comma instead of )

[jakobnissen]

In the example:

julia> foo(a b)
ERROR: ParseError:
# Error @ REPL[2]:1:7
foo(a b)
#     ╙ ── Expected `)`

It would be better to suggest adding a , rather than a ). I don't know if this is feasible since it probably requires parsing ahead in front of the parser error to find the missing )

[KristofferC]

Dup of #313