[#15] Added ‘Support the Campaign’ button to social links

data/de/share/7-support.yaml

@@ -0,0 +1,5 @@
+id: support
+name: Unterstützen Sie die Kampagne
+titleBefore: Auf
+titleAfter: teilen
+link: https://fsfe.org/donate

data/en/share/7-support.yaml

@@ -0,0 +1,5 @@
+id: support
+name: Support the Campaign
+titleBefore: Support the Campaign
+titleAfter: 
+link: https://fsfe.org/donate

static/css/custom.css

@@ -245,3 +245,6 @@ aside.sharecolumn a#gplus-left {
 aside.sharecolumn a#facebook-left {
   background-image: url("/img/share/facebook_white.png");
 }
+aside.sharecolumn a#support-left {
+  background-image: url("/img/share/support_red.png");
+}