Added Hackerrank profile

css/brands.css

@@ -483,6 +483,16 @@ button:hover,
   filter: brightness(90%);
 }
 
+/* Hackerrank */
+.button.button-hackerrank {
+  color: #ffffff;
+  background-color: #32c766;
+}
+.button.button-hackerrank:hover,
+.button.button-hackerrank:focus {
+  filter: brightness(90%);
+}
+
 /* Hedgedoc */
 .button.button-hedgedoc {
   color: #ffffff;