add attribution for self host instance

docker/attribution/en.js

@@ -0,0 +1,14 @@
+// Self-host attribution line, copied into /app/languages/en/ at image build.
+//
+// The license of Adventure Land requires a crawlable link back to
+// https://adventure.land and forbids implying that the original project
+// supports a self-hosted instance. docker/patch-attribution.js points the
+// login/selection help box at this phrase instead of the upstream
+// "Email, for anything" line.
+//
+// English is also the fallback for every language without its own
+// attribution.json, so keep the markup identical to docker/attribution/de.json.
+module.exports = {
+	"pages.attribution.self-hosted":
+		'Self-hosted version of Adventure Land.<br>Original &amp; license: <a target="_blank" rel="noopener" class="cancela eexternal" style="display: inline; color: #33BF6D" href="https://adventure.land">adventure.land</a><br>No support by the original project.',
+};