Restrict to allowed extensions

src/main/kotlin/main/Main.kt

@@ -163,6 +163,7 @@ fun app() {
 fun selectFile(extensions: Set<String>, onFileSelected: (String) -> Unit) {
     val fileDialog = FileDialog(Frame(), "Select a file", FileDialog.LOAD)
     fileDialog.isMultipleMode = false // To enable selecting only one file
+    fileDialog.file = "." + extensions.joinToString(";.")
     fileDialog.isVisible = true
 
     val selectedFile = fileDialog.file