support live_file_input

[bcardarella]

Now that @carson-katri is testing out Core for 0.4 we need a version of live_file_input for eac client. These should really go in the client's Component module but just tracking here.

See original: https://github.com/phoenixframework/phoenix_live_view/blob/v0.20.17/lib/phoenix_component.ex#L2903-L2922

@carson-katri do you have a good idea on what the SwiftUI view should be in place of the html input type=file ?

[carson-katri]

fileImporter is the modifier used for selecting files:
https://developer.apple.com/documentation/swiftui/view/fileimporter(ispresented:allowedcontenttypes:oncompletion:)

We can make the generated component add that modifier automatically.