Add `julia-repl` to matched fenced-code languages.

[NHDaly]

Make the julia fenced-code regex also match julia-repl, which is sometimes used to indicate that a code-block contains output from a julia REPL session (i.e. the julia> input prompt).

Here is an example of this being encouraged from the Julia documentation: https://docs.julialang.org/en/latest/manual/documentation/#Documentation-1

Currently, adding a - in the language specification seems to break parsing completely, such that the parser stops highlighting after it, which is a worse failure than simply not understanding the language:

The goal of this PR is to fix that! :)

[NHDaly]

Thanks much! :)

[burodepeper]

You too!