Add pl translation for search placeholder (#2090)

Author: katafrakt

quartz/i18n/locales/pl-PL.ts

@@ -51,7 +51,7 @@ export default {
     },
     search: {
       title: "Szukaj",
-      searchBarPlaceholder: "Search for something",
+      searchBarPlaceholder: "Wpisz frazę wyszukiwania",
     },
     tableOfContents: {
       title: "Spis treści",