[translation] Add Polish language (#243)

* Add polish translation file

* Add polish to other translations

Author: pktiuk

messages/de-DE.json

@@ -301,6 +301,7 @@
     "es": "Español",
     "de-DE": "Deutsch",
     "zh-CN": "Chinese (Simplified)",
+    "pl-PL": "Polski",
     "ru-RU": "Русский",
     "it-IT": "Italiano",
     "ua-UA": "Українська"

messages/en-US.json

@@ -301,6 +301,7 @@
     "es": "Español",
     "de-DE": "Deutsch",
     "zh-CN": "Chinese (Simplified)",
+    "pl-PL": "Polski",
     "ru-RU": "Русский",
     "it-IT": "Italiano",
     "ua-UA": "Українська"

messages/es.json

@@ -302,6 +302,7 @@
     "es": "Español",
     "de-DE": "Deutsch",
     "zh-CN": "Chinese (Simplified)",
+    "pl-PL": "Polski",
     "ru-RU": "Русский",
     "it-IT": "Italiano",
     "ua-UA": "Українська"

messages/fi.json

@@ -301,6 +301,7 @@
     "es": "Español",
     "de-DE": "Deutsch",
     "zh-CN": "Chinese (Simplified)",
+    "pl-PL": "Polski",
     "ru-RU": "Русский",
     "it-IT": "Italiano",
     "ua-UA": "Українська"

messages/fr-FR.json

@@ -301,6 +301,7 @@
     "es": "Español",
     "de-DE": "Deutsch",
     "zh-CN": "Chinese (Simplified)",
+    "pl-PL": "Polski",
     "ru-RU": "Русский",
     "it-IT": "Italiano",
     "ua-UA": "Українська"

messages/it-IT.json

@@ -301,6 +301,7 @@
     "es": "Español",
     "de-DE": "Deutsch",
     "zh-CN": "Chinese (Simplified)",
+    "pl-PL": "Polski",
     "ru-RU": "Русский",
     "it-IT": "Italiano",
     "ua-UA": "Українська"