Add the Paiwan language (pwn)

Requested at
https://translatewiki.net/wiki/Thread:Support/_Wp/pwn_Translation_of_MediaWiki_(most_important_messages)

Autonym verified with Paiwan dictionary by Raliegh Ferrell
( https://archive.org/details/paiwandictionary0000ferr )
and the online dictionary on the website of Taiwan's
Council of Indigenous People
( https://e-dictionary.apc.gov.tw/pwn/search.htm ).
It's also confirmed at
https://incubator.wikimedia.org/w/index.php?oldid=5144344#The_name_of_the_Paiwan_language_in_itself

data/language-data.json

@@ -3124,6 +3124,13 @@
             ],
             "português"
         ],
+        "pwn": [
+            "Latn",
+            [
+                "AS"
+            ],
+            "pinayuanan"
+        ],
         "qu": [
             "Latn",
             [