Add polish to processing lanugages

SOLR doesn't support polish out of the box. Plugins are required for
polish. The language has been added only with basic support. For
better results, a manual setup of solr is required.

Closes: #1345

modules/fts-psql/src/main/scala/docspell/ftspsql/FtsRepository.scala

@@ -194,5 +194,6 @@ object FtsRepository extends DoobieMeta {
       case Language.Japanese   => "simple"
       case Language.Hebrew     => "simple"
       case Language.Lithuanian => "simple"
+      case Language.Polish     => "simple"
     }
 }