io/input,io/clipboard: [API] replace WriteOp with command

Signed-off-by: Elias Naur <mail@eliasnaur.com>

widget/selectable.go

@@ -2,6 +2,7 @@ package widget
 
 import (
 	"image"
+	"io"
 	"math"
 	"strings"
 
@@ -332,7 +333,7 @@ func (e *Selectable) command(gtx layout.Context, k key.Event) {
 		case "C", "X":
 			e.scratch = e.text.SelectedText(e.scratch)
 			if text := string(e.scratch); text != "" {
-				clipboard.WriteOp{Text: text}.Add(gtx.Ops)
+				gtx.Queue(clipboard.WriteCmd{Type: "application/text", Data: io.NopCloser(strings.NewReader(text))})
 			}
 		// Select all
 		case "A":