Add 404 page.

Change-Id: Id0c59bceacb2ffb3e9dbf81f8f25d9dce39cc955
diff --git a/404.md b/404.md
new file mode 100644
index 0000000..129881e
--- /dev/null
+++ b/404.md
@@ -0,0 +1,11 @@
+---
+layout: page
+title: Not Found
+permalink: /404.html
+---
+
+# 404
+
+Page not found.
+
+Try the <a href="https://twrp.me/Devices">devices</a> page to look for another device.