Add .kdenlive project files to the list of allowed clips in a project

BUG: 408299

src/dialogs/clipcreationdialog.cpp

@@ -62,7 +62,7 @@ QStringList ClipCreationDialog::getExtensions()
 {
     // Build list of MIME types
     QStringList mimeTypes = QStringList() << QStringLiteral("") << QStringLiteral("application/x-kdenlivetitle") << QStringLiteral("video/mlt-playlist")
-                                          << QStringLiteral("text/plain");
+                                          << QStringLiteral("text/plain") << QStringLiteral("application/x-kdenlive");
 
     // Video MIMEs
     mimeTypes << QStringLiteral("video/x-flv") << QStringLiteral("application/vnd.rn-realmedia") << QStringLiteral("video/x-dv") << QStringLiteral("video/dv")