Add Nigerian Pidgin (pcm)

Requested at
https://translatewiki.net/wiki/Thread:Support/_pcm_Activate_new_language:_Nigerian_Pidgin_-_%27Naij%C3%A1%27

There's also an active Wikipedia Incubator in it.

The autonym Naijá is used in Ethnologue and also in this article:
https://ifra-nigeria.org/ongoing-research-programs/naijasyncor/naija-languej-akedemi

I also verified it with several other experienced Nigerian
Wikipedians and they confirmed it.

data/langdb.yaml

@@ -467,6 +467,7 @@ languages:
   pap-aw: [Latn, [AM], Papiamento]
   pbb: [Latn, [AM], Nasa Yuwe]
   pcd: [Latn, [EU], Picard]
+  pcm: [Latn, [AF], Naijá]
   pdc: [Latn, [EU, AM], Deitsch]
   pdt: [Latn, [EU, AM], Plautdietsch]
   pfl: [Latn, [EU], Pälzisch]

data/language-data.json

@@ -3006,6 +3006,13 @@
             ],
             "Picard"
         ],
+        "pcm": [
+            "Latn",
+            [
+                "AF"
+            ],
+            "Naijá"
+        ],
         "pdc": [
             "Latn",
             [
@@ -5577,6 +5584,7 @@
         ],
         "NG": [
             "en",
+            "pcm",
             "ha",
             "ig",
             "yo",