desktop: files Drag & Drop support (#2843)

* desktop: files Drag&Drop support

* reduce diff

* move

* move 2

* move 3

---------

Co-authored-by: Evgeny Poberezkin <2769109+epoberezkin@users.noreply.github.com>

apps/multiplatform/common/src/desktopMain/kotlin/chat/simplex/common/platform/Modifier.desktop.kt

@@ -1,7 +1,8 @@
 package chat.simplex.common.platform
 
 import androidx.compose.runtime.Composable
-import androidx.compose.ui.Modifier
+import androidx.compose.ui.*
+import androidx.compose.ui.graphics.painter.Painter
 
 actual fun Modifier.navigationBarsWithImePadding(): Modifier = this
 
@@ -13,3 +14,18 @@ actual fun ProvideWindowInsets(
 ) {
   content()
 }
+
+@Composable
+actual fun Modifier.desktopOnExternalDrag(
+  enabled: Boolean,
+  onFiles: (List<String>) -> Unit,
+  onImage: (Painter) -> Unit,
+  onText: (String) -> Unit
+): Modifier =
+onExternalDrag(enabled) {
+  when(val data = it.dragData) {
+    is DragData.FilesList -> onFiles(data.readFiles())
+    is DragData.Image -> onImage(data.readImage())
+    is DragData.Text -> onText(data.readText())
+  }
+}