Add basics for contribution details

Route, controller, links, selected property/styles, etc.

app/styles/components/_contribution-list.scss

@@ -37,6 +37,7 @@ ul.contribution-list {
     background-color: rgba(255,255,255,0.1);
     font-size: 1.2rem;
     border-bottom: 1px solid rgba(255,255,255,0.2);
+    cursor: pointer;
 
     &:first-of-type {
       border-top: 1px solid rgba(255,255,255,0.2);
@@ -52,6 +53,10 @@ ul.contribution-list {
       opacity: 0.6;
     }
 
+    &.selected {
+      background-color: rgba(255,255,255,0.2);
+    }
+
     p {
       align-self: center;
       margin: 0;