feat(path): add entry to PATH if non existant

[JanDeDobbeleer]

resolves #62

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[trajano]

Yup this does the first request which is to check for existence, but I think we can make it more shell/platform neutral by creating the directory if it can be configured to do so.

[JanDeDobbeleer]

@trajano imho, creating a directory is no use-case here. That's beyond the scope of aliae. You can add that to the script block. I'm going to be strict in what we can or can't do, because otherwise this will become a dragon of a tool.