Add placeholder for smartcard manual

This prepares a new DocAction for Smartcard Management.

src/kleopatra.rc

 <!DOCTYPE gui >
-<gui name="kleopatra" version="510" >
+<gui name="kleopatra" version="511" >
     <MenuBar>
         <Menu name="file">
             <text>&amp;File</text>
@@ -93,6 +93,7 @@
             <Action name="help_doc_quickguide"/>
             <Action name="help_doc_compendium"/>
             <Action name="help_doc_symenc"/>
+            <Action name="help_doc_smartcard"/>
             <Action name="help_doc_vsa10573"/>
             <Action name="help_doc_vsa10584"/>
             <Separator/>

src/mainwindow.cpp

@@ -617,6 +617,12 @@ void MainWindow::Private::setupActions()
             QStringLiteral("../share/doc/gnupg-vsd"));
     coll->addAction(QStringLiteral("help_doc_vsa10584"), vsa10584);
 
+    const auto smartcard = new DocAction(QIcon::fromTheme(QStringLiteral("dvipdf")), i18n("Smartcard Management"),
+            i18nc("Only available in German and English. Leave to English for other languages.",
+                "smartcard_howto_de.pdf"),
+            QStringLiteral("../share/doc/gnupg-vsd"));
+    coll->addAction(QStringLiteral("help_doc_smartcard"), smartcard);
+
     const auto man_gpg = new DocAction(QIcon::fromTheme(QStringLiteral("help-contextual")), i18n("GnuPG Manual"),
             QStringLiteral("gnupg.pdf"), QStringLiteral("../share/doc/gnupg"));
     coll->addAction(QStringLiteral("help_doc_gnupg"), man_gpg);