Add io.WriterAt to File interface

Signed-off-by: Paulo Gomes <[email protected]>

Author: pjbgf

fs.go

@@ -166,8 +166,7 @@ type File interface {
 	// Name returns the name of the file as presented to Open.
 	Name() string
 	io.Writer
-	// TODO: Add io.WriterAt for v6
-	// io.WriterAt
+	io.WriterAt
 	io.ReaderAt
 	io.Seeker
 	// Lock locks the file like e.g. flock. It protects against access from