created directory for dialogs

src/widgets/dialogs/WelcomeDialog.cpp

@@ -0,0 +1,13 @@
+#include "WelcomeDialog.hpp"
+
+namespace chatterino {
+namespace widgets {
+
+WelcomeDialog::WelcomeDialog()
+    : BaseWindow(nullptr, BaseWindow::EnableCustomFrame)
+{
+    this->setWindowTitle("Chatterino quick setup");
+}
+
+}  // namespace widgets
+}  // namespace chatterino