Refactor `explore:*`

app/assets/javascripts/pages/explore/groups/index.js

+import GroupsList from "~/groups_list";
+import Landing from "~/landing";
+
+export default function() {
+  new GroupsList();
+  const landingElement = document.querySelector(".js-explore-groups-landing");
+  if (!landingElement) return;
+  const exploreGroupsLanding = new Landing(
+    landingElement,
+    landingElement.querySelector(".dismiss-button"),
+    "explore_groups_landing_dismissed"
+  );
+  exploreGroupsLanding.toggle();
+}

app/assets/javascripts/pages/explore/projects/index.js

+import ProjectsList from "~/projects_list";
+
+export default function() {
+  new ProjectsList();
+}