Add direnv support as an opt-in?

[bicycle1885]

I often add the following configuration file (.envrc) to a package repository in order to activate a
package-local environment using direnv:

.envrc:

export JULIA_PROJECT=@.

I know this is not so widely used but I think it would be nice to have it as an opt-in feature of package generation. If you like the idea, I'm happy to create a pull request.

[christopher-dG]

This could be a plugin, but I don't recommend opening a PR until I get around to finishing up #61.

[bicycle1885]

Okay, thank you for your comment.