Hide register page when registrations are closed

- Improve UX for "private" instances.

templates/auth/register/main.scss

@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2022  Aravinth Manivannan <realaravinth@batsense.net>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+@import '../../components/table/main';
+
+.reg-closed__table {
+  @include table;
+  margin: auto;
+}
+
+.reg-closed__table-title-text {
+  @include table__title-text;
+}
+
+.reg-closed__body-text {
+  display: block;
+  margin: 0.5em 0;
+}