recognise julia code in docstrings

[dahtah]

When using Documenter.jl for package docs, there is the option of including example code in a function's docstring by enclosing it with backticks. It'd be nice of julia-snail could recognise it as code instead of comment, so the user could hit C-c C-l for instance to test the example directly in the REPL. emacs-ess implements something similar for R's docstrings. I feel like this can be implemented relatively easily by fiddling with the syntax table somewhere?

Extra credit if julia-snail can manage to insert the correct "@jldoctest" output automatically.