add simple way of comparing taxonomy between catalogs

Closes #121

This MR allows to display side by side two taxonomical distribution.

frontend/src/components/Navbar.vue

@@ -33,6 +33,7 @@ export default {
       items: [
         { title: 'Home', icon: 'fa-home', route: '/' },
         { title: 'Catalog Statistics', icon: 'far fa-chart-bar', route: '/stats' },
+        { title: 'Compare Taxonomy', icon: 'far fa-clone', route: '/compare' },
         { title: 'Genes', icon: 'format_list_bulleted', route: '/genes' },
         { title: 'About', icon: 'contact_support', route: '/about' },
       ],