Enable i18n for Polish language

frontend/angular.json

@@ -71,6 +71,10 @@
             "translation": "src/locale/messages.nb.xlf",
             "baseHref": "/nb/"
           },
+          "pl": {
+            "translation": "src/locale/messages.pl.xlf",
+            "baseHref": "/pl/"
+          },
           "pt": {
             "translation": "src/locale/messages.pt.xlf",
             "baseHref": "/pt/"

frontend/src/app/app.constants.ts

@@ -71,7 +71,7 @@ export const languages: Language[] = [
    { code: 'ja', name: '日本語' },          // Japanese
    { code: 'nb', name: 'Norsk' },           // Norwegian Bokmål
 // { code: 'nn', name: 'Norsk Nynorsk' },   // Norwegian Nynorsk
-// { code: 'pl', name: 'Polski' },          // Polish
+   { code: 'pl', name: 'Polski' },          // Polish
    { code: 'pt', name: 'Português' },       // Portuguese
 // { code: 'pt-BR', name: 'Português (Brazil)' }, // Portuguese (Brazil)
 // { code: 'ro', name: 'Română' },          // Romanian