Add subtitle actions in Project menu

src/kdenliveui.rc

 <!DOCTYPE kpartgui SYSTEM "kpartgui.dtd">
-<kpartgui name="kdenlive" version="194" translationDomain="kdenlive">
+<kpartgui name="kdenlive" version="195" translationDomain="kdenlive">
   <MenuBar>
     <Menu name="file" >
       <Action name="file_save"/>
@@ -27,6 +27,10 @@
       <Action name="download_resource" /> 
       <Menu name="generators" ><text>Generators</text>
       </Menu>
+      <Menu name="subtitles" ><text>Subtitles</text>
+          <Action name="subtitle_tool" />
+          <Action name="add_subtitle" />
+      </Menu>
       <Separator />
       <Action name="bin_view_mode" />
       <Action name="stopmotion" />

src/mainwindow.cpp

@@ -4182,6 +4182,9 @@ void MainWindow::slotEditSubtitle()
 
 void MainWindow::slotAddSubtitle()
 {
+    if (pCore->currentDoc()->getSubtitleModel() == nullptr) {
+        slotEditSubtitle();
+    }
     getCurrentTimeline()->controller()->addSubtitle();
 }