Add select directory feature

[wenshuishi]

Fix this issue: #18

[br14n-sol]

Hi, first of all thanks for contributing 👍

I'm not sure about adding it as a default behavior, so far only file selection has been allowed, so it would result in unexpected behavior for anyone using the package from previous versions.

[br14n-sol]

I was thinking of adding it along with a configuration option, something like this:

expected?: 'file' | 'directory' | 'both'

Being by default the value of: 'file'

[br14n-sol]

This is just something I thought of just now, if you have a better idea comment it.

[wenshuishi]

Hi, first of all thanks for contributing 👍

I'm not sure about adding it as a default behavior, so far only file selection has been allowed, so it would result in unexpected behavior for anyone using the package from previous versions.

Thanks for reply, yes, you are right, maybe give users an option is better.

[wenshuishi]

I was thinking of adding it along with a configuration option, something like this:

expected?: 'file' | 'directory' | 'both'

Being by default the value of: 'file'

Ok, i have submitted another pull request for that:
you decide whether to merge it, or you can implement it yourself, if you have any better ideas.