Improved releasenotes manual can also be opened from a databasewindow now.

pglab/About.cpp

@@ -1,7 +1,9 @@
 #include "About.h"
 #include <QCoreApplication>
+#include <QDesktopServices>
 #include <QMessageBox>
 #include <QString>
+#include <QUrl>
 
 void ShowAboutDialog(QWidget *parent)
 {
@@ -21,3 +23,8 @@ void ShowAboutDialog(QWidget *parent)
               "attribution 3.0 license.</p>"
               ).arg(year).arg(releaseNotesUrl).arg(pgLabVersionString));
 }
+
+void OpenManual()
+{
+    QDesktopServices::openUrl(QString("https://eelke.gitlab.io/pgLab/#pglab-user-manual"));
+}