translation: Create Polish translation style guide.

Add general notes on Polish translation.
Translate special terms used in Zulip.

docs/polish.md

@@ -0,0 +1,66 @@
+# Polish translation style guide
+
+Use semi-formal Polish for translation, some specifics:
+
+  * informal "you" (*ty*) instead of more formal approaches (e.g. plural "you" (*wy*), using any formal titles like *Państwo*, *Pan/Pani*)
+
+  * imperative, active and continuous verbs, e.g. *manage streams* - *zarządzaj kanałami*, not *zarządź kanałami*
+
+  * not using reflexive *się*, e.g. *log out* would be simply *wyloguj*, not *wyloguj się*
+
+  * warm and friendly phrasing whenever appropriate
+
+  * no slang or regional phrases that could be unclear or too informal, e.g. *zajawka*
+
+  * consistent usage of Zulip-specific terms and common verbs for actions, even if it means repeating - this is one of the key aspects of "semi-formal", as synonyms would be often more appropriate in written Polish
+
+  * mindful usage of long words and phrases - it's sometimes hard to translate English to Polish concisely, be mindful of how it looks on the frontend after translating
+
+  * balance common verbs and nouns with specific IT-related translation of English terms - this can be tricky, try to check how other resources were translated (e.g. GMail, Microsoft websites, Facebook) to decide what wouldn't sound awkward in Polish
+
+Some terms are very tricky to translate, so be sure to communicate with other Polish speakers in the community. It's all about making Zulip friendly and usable.
+
+# Common translations
+
+## Special terms used in Zulip
+**customization**: personalizacja, *kastomizacja* could be too awkward and *dostosowanie do potrzeb klienta* is too long
+
+**emoji**: emoji, both in singular and plural, *ikona emoji* is a pleonasm
+
+**filter**: filtr (noun) and filtrowanie (verb)
+
+**group PM**: czat grupowy, different from *wiadomość* since the usage of *czat grupowy* seems more common
+
+**home**: strona główna
+
+**me**: me, no translation since it's used as `/me`
+
+**mention**: mention, translation as *wzmianka* or *wskazanie* wouldn't convey the meaning
+
+**message table**: lista wiadomości
+
+**muting a stream**: wyciszenie wątku
+
+**narrow**: zawężenie (noun) and zawęzić (verb)
+
+**pinning**: przypięcie (noun) and przypiąć (verb)
+
+**private message**: prywatna wiadomość
+
+**PM**: PM, translation could be confusing
+
+**private stream**: prywatny kanał
+
+**realm**: domena
+
+**stream**: kanał, similar to a tv channel - *strumień* sounds a bit artificial
+
+**subscribing to a stream**: (za)subskrybowanie kanału (noun) and (za)subskrybować kanał (verb), perfective form depending on the context
+
+**topic**: wątek
+
+**unsubscribing from a stream**: odsubskrybowanie kanału (noun) and odsubskrybować kanał (verb)
+
+**view**: widok
+
+**starred message**: oznaczona wiadomość

docs/translating.md

@@ -27,6 +27,7 @@ We are building a collection of translation style guides for Zulip,
 giving guidance on how Zulip should be translated into specific
 languages (e.g. what word to translate words like "home" to):
 
+* [Polish](polish.html)
 * [Spanish](spanish.html)
 
 ## Setting Default Language in Zulip