Add translation into Polish

CHANGES.rst

@@ -5,6 +5,7 @@ www.gafam.info CHANGES
 
 in progress
 -----------
+- Add translation into Polish. Thanks, Piotr and friends!
 
 2018-02-06 0.6.0
 ----------------

htdocs/index.html

@@ -561,7 +561,7 @@
 
             In the beginning, we had French, English and German as translated by the people of LQDN.
             As of now, we have been able to add translations into Japanese, Esperanto, Russian
-            (half-finished), Mandarin Chinese and Italian from the community. Thank you so much!
+            (half-finished), Mandarin Chinese, Italian and Polish from the community. Thank you so much!
         </p>
 
         <p class="content is-spaced">

src/js/main.js

@@ -59,6 +59,10 @@ $(document).ready(function() {
                 "type": "it",
                 "label": "Italian",
                 "path": "po/it.po"
+            }, {
+                "type": "pl",
+                "label": "Polish",
+                "path": "po/pl.po"
             }
         ]
     });