[Web, Rspamd] Add bad language map, add map to mailcow UI

data/conf/rspamd/custom/bad_languages.map

@@ -0,0 +1 @@
+# Regex! /de/ will also match /de_at/ etc.

data/conf/rspamd/local.d/multimap.conf

@@ -127,3 +127,12 @@ BAD_WORDS_DE {
   regexp = true;
   score = 0.1;
 }
+
+BAD_LANG {
+  type = 'selector';
+  selector = 'languages';
+  map = "${LOCAL_CONFDIR}/custom/bad_languages.map";
+  symbols_set = ["LANG_FILTER"];
+  regexp = true;
+  score = 5.0;
+}