file selector
Factory
The $create() factory method instantiates a FileSelector given the 3 fields
described below.
Fields
base_dir: The directory in which to select files. If the path exists but doesn't point to a directory, this should be an error.allow_not_found: The behavior ifbase_dirdoesn't exist in the filesystem. IfFALSE, an error is returned. IfTRUE, an empty selection is returnedrecursive: Whether to recurse into subdirectories.