Tweak warning about local directories

[fredrikekre]

This warning

Pkg.jl/src/REPLMode/argument_parsers.jl

Line 465 in 77db067

@info "Use `./$word` to add or develop the local directory at `$(Base.contractuser(abspath(word)))`."

is a bit annoying on case insensitive filesystems since e.g. pkg> add Test will show it if you have a test folder. Could at least be made case-sensitive or even better perhaps check if the folder is actually a package folder.