fix: Focus accessibility (#1536)

* fix: Focus ring appearing on click
fix: Focus ring not appearing on sidebar links
add: focus-visible polyfill

* fix: More visible outlines on keyboard focus
fix: Header block should be a button semantically

app/components/TeamLogo.js

@@ -6,7 +6,7 @@ const TeamLogo = styled.img`
   height: 38px;
   border-radius: 4px;
   background: ${(props) => props.theme.background};
-  border: 1px solid ${(props) => props.theme.divider};
+  outline: 1px solid ${(props) => props.theme.divider};
 `;
 
 export default TeamLogo;