app: move system.ClipboardEvent to its own package

API change. Update your code with gofmt rule and goimports:

gofmt -r "system.ClipboardEvent -> clipboard.Event"
goimports

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

app/internal/window/os_ios.go

@@ -38,6 +38,7 @@ import (
 	"unsafe"
 
 	"gioui.org/f32"
+	"gioui.org/io/clipboard"
 	"gioui.org/io/key"
 	"gioui.org/io/pointer"
 	"gioui.org/io/system"
@@ -223,7 +224,7 @@ func onTouch(last C.int, view, touchRef C.CFTypeRef, phase C.NSInteger, x, y C.C
 func (w *window) ReadClipboard() {
 	runOnMain(func() {
 		content := nsstringToString(C.gio_readClipboard())
-		w.w.Event(system.ClipboardEvent{Text: content})
+		w.w.Event(clipboard.Event{Text: content})
 	})
 }