[UXTHEME] Add Polish (pl-PL) translation (#8913)

Polish translations in uxtheme (for appearance tab in the desktop properties).

dll/win32/uxtheme/lang/pl-PL.rc

@@ -0,0 +1,19 @@
+/*
+ * PROJECT:     ReactOS uxtheme.dll
+ * LICENSE:     LGPL-2.1-or-later (https://spdx.org/licenses/LGPL-2.1-or-later)
+ * PURPOSE:     Polish resource file
+ * TRANSLATOR:  Copyright 2026 Karol Gocłowski <[email protected]>
+ */
+
+LANGUAGE LANG_POLISH, SUBLANG_DEFAULT
+
+/* Strings */
+
+STRINGTABLE
+BEGIN
+    IDS_MESSAGEBOX "Okno komunikatu"
+    IDS_ACTIVEWIN "Aktywne okno"
+    IDS_INACTIVEWIN "Nieaktywne okno"
+    IDS_OK "OK"
+    IDS_WINTEXT "Tekst okna"
+END

dll/win32/uxtheme/uxtheme.rc

@@ -28,6 +28,9 @@
 #ifdef LANGUAGE_EN_US
     #include "lang/en-US.rc"
 #endif
+#ifdef LANGUAGE_PL_PL
+    #include "lang/pl-PL.rc"
+#endif
 #ifdef LANGUAGE_PT_BR
     #include "lang/pt-BR.rc"
 #endif