UI: Add file picker when creating a file source

[hariso]

DeVaris commented in https://www.notion.so/Conduit-Testing-48d24d2c15b64b4a82e478a39a5d3527?d=cdfdea66aa0d445f801fd2d53849c545#fbbd714f66e94706b3dff24613108c05

If someone choose a file connector we should present a file picker.

[jmar910]

@hariso The full path to the file from the browser is blocked for security reasons, we will have to think of another solution here or leave as is.

[simonl2002]

We will not be doing this in the foreseeable future given the technical limitations going to close.