Desktop: Add Button and Link to 'Contribute' Page.

Add a button that opens the 'Contribute' page to the 'About' dialogue,
to encourage more users to start to contribute.

Requires https://github.com/subsurface/new-website/pull/36 to be
deployed to have a valid link target.

Signed-off-by: Michael Keller <mikeller@042.ch>

CHANGELOG.md

@@ -1,3 +1,4 @@
+desktop: add a button linking to the 'Contribute' page
 desktop: fix gas switches in UDDF exports
 core: allow of up to 6 O2 sensors (and corresponding voting logic)
 desktop: add divemode as a possible dive list column

desktop-widgets/about.cpp

@@ -30,12 +30,17 @@ void SubsurfaceAbout::on_licenseButton_clicked()
 	QDesktopServices::openUrl(QUrl("http://www.gnu.org/licenses/gpl-2.0.txt"));
 }
 
+void SubsurfaceAbout::on_contributeButton_clicked()
+{
+	QDesktopServices::openUrl(QUrl("http://subsurface-divelog.org/contribute/"));
+}
+
 void SubsurfaceAbout::on_websiteButton_clicked()
 {
-	QDesktopServices::openUrl(QUrl("http://subsurface-divelog.org"));
+	QDesktopServices::openUrl(QUrl("http://subsurface-divelog.org/"));
 }
 
 void SubsurfaceAbout::on_creditButton_clicked()
 {
-	QDesktopServices::openUrl(QUrl("http://subsurface-divelog.org/misc/credits"));
+	QDesktopServices::openUrl(QUrl("http://subsurface-divelog.org/credits/"));
 }

desktop-widgets/about.h

@@ -13,6 +13,7 @@ public:
 private
 slots:
 	void on_licenseButton_clicked();
+	void on_contributeButton_clicked();
 	void on_websiteButton_clicked();
 	void on_creditButton_clicked();
 

desktop-widgets/about.ui

@@ -91,6 +91,13 @@
        </property>
       </widget>
      </item>
+     <item>
+      <widget class="QPushButton" name="contributeButton">
+       <property name="text">
+        <string>C&amp;ontribute</string>
+       </property>
+      </widget>
+     </item>
      <item>
       <widget class="QPushButton" name="websiteButton">
        <property name="text">
@@ -125,6 +132,7 @@
  <tabstops>
   <tabstop>licenseButton</tabstop>
   <tabstop>creditButton</tabstop>
+  <tabstop>contributeButton</tabstop>
   <tabstop>websiteButton</tabstop>
   <tabstop>closeButton</tabstop>
  </tabstops>