feat: allow returning multiple directories

[LuisMayo]

This PR adds the ability for the library to locate many valid installations, which may be useful, specially on Linux installations. As discussed here: #17 (comment)

I'm really a newbie when it comes to Rust so I'd be happy to fix any problems you may encounter and thanks for your work!

[amtep]

Just wanted to let you know that I'm also waiting for this feature :)

My use case is that I want to find a particular game, regardless of in which installation it's installed.
So I'll loop over the steamdirs until the find_app resolves.

I looked at the code and wondered, is it really an error if no installations are found? I figure it could just return an empty Vec in that case.

[LuisMayo]

Just wanted to let you know that I'm also waiting for this feature :)

My use case is that I want to find a particular game, regardless of in which installation it's installed. So I'll loop over the steamdirs until the find_app resolves.

I looked at the code and wondered, is it really an error if no installations are found? I figure it could just return an empty Vec in that case.

That's actually the very same reason I want it. My app patches a Videogame (VHS) and I want to locate it to patch the exe, no matter the install dir

About returning on Error I just made it to be consistent with the locate function, but it's true that it may not make that much sense, so I could change it to return an empty array, I don't have strong feelings towards any of the options.