Add opensearch declaration (#1058)

* feat: Add opensearch declaration

* cleanup

---------

Co-authored-by: Johannes Zorn <johannes.zorn@zollsoft.com>
Co-authored-by: Sascha Ißbrücker <sascha.issbruecker@gmail.com>

bookmarks/views/opensearch.py

@@ -0,0 +1,18 @@
+from django.urls import reverse
+from django.shortcuts import render
+
+
+def opensearch(request):
+    base_url = request.build_absolute_uri(reverse("linkding:root"))
+    bookmarks_url = request.build_absolute_uri(reverse("linkding:bookmarks.index"))
+
+    return render(
+        request,
+        "opensearch.xml",
+        {
+            "base_url": base_url,
+            "bookmarks_url": bookmarks_url,
+        },
+        content_type="application/opensearchdescription+xml",
+        status=200,
+    )