Add missing CSS for ribbons (#4159)

Author: aneta-petrova

web/content/css/_ribbon.scss

@@ -144,3 +144,17 @@ SOFTWARE.
   -o-transform: rotate(-45deg);
   transform: rotate(-45deg);
 }
+
+.release-ribbon {
+  @extend .github-fork-ribbon;
+  &:before {
+    background-color: #a00;
+  }
+}
+
+.issue-ribbon {
+  @extend .github-fork-ribbon;
+  &:before {
+    background-color: #025d8c;
+  }
+}