[Feature] Add Check If Directory Exists and File Copy to StorageFileHelper

[bolyb]

Describe the problem this feature would solve

The toolkit StorageFileHelper still lacks many common file functions that are found in other Microsoft storage APIs.

Describe the solution

It would be nice if the StorageFileHelper had more features for common file-system operations, such as checking if a directory exists, creating a directory if it does not exist, and copying a file from one directory to another.

Describe alternatives you've considered

I have tried using other storage APIs, however these APIs are not authorized to operate inside StorageFolder KnownFolder locations (such as the user's documents library) in a UWP app.

Hello, 'bolyb! Thanks for submitting a new feature request. I've automatically added a vote 👍 reaction to help get things started. Other community members can vote to help us prioritize this feature in the future!

[Kyaa-dost]

Hi @bolyb, Thanks for considering these options. Is this something you can work on? Also, Let's see what our devs think about this proposal.

[RobbyRobbyRobby]

Can I suggest this might get everyone started:

TryGetItemAsync()

Returns null instead of raising an exception.

[Kyaa-dost]

Transferring this to the discussion as it still requires insight from the community.