chore: Update

sink.go

@@ -2,6 +2,7 @@ package uio
 
 type Sink interface {
 	Write(src []byte) (n int, err error)
+	WriteFully(src []byte) error
 }
 
 type BufferedSink interface {

source.go

@@ -2,6 +2,7 @@ package uio
 
 type Source interface {
 	Read(dst []byte) (n int, err error)
+	ReadFully(dst []byte) error
 }
 
 type BufferedSource interface {