fix: accessiblity improvements, focus states, real buttons

app/components/Tab.js

@@ -2,6 +2,7 @@
 import * as React from 'react';
 import styled, { withTheme } from 'styled-components';
 import { NavLink } from 'react-router-dom';
+import { lighten } from 'polished';
 
 type Props = {
   theme: Object,
@@ -23,6 +24,13 @@ const StyledNavLink = styled(NavLink)`
     border-bottom: 3px solid ${props => props.theme.divider};
     padding-bottom: 5px;
   }
+
+  &:focus {
+    outline: none;
+    border-bottom: 3px solid
+      ${props => lighten(0.4, props.theme.buttonBackground)};
+    padding-bottom: 5px;
+  }
 `;
 
 function Tab(props: Props) {