Add Upper and Lower Sorbian language versions

frontend/dsb/catalogue.json

@@ -0,0 +1,10 @@
+{
+    "catalogue": {
+        "volume": "Band",
+        "public": "\u00d6ffentlich",
+        "not_public": "Nicht \u00f6ffentlich",
+        "title_main": "Museum-Digital",
+        "title_sub": "Objektkatalog f\u00fcr",
+        "generated": "Erzeugt"
+    }
+}