Add the Bulu language (bum)

Requested for translatewiki at
https://translatewiki.net/wiki/Thread:User_talk:KrystjanM/Request_to_translate_MediaWiki_into_Bulu(B%C3%BAl%C3%B9)_language

Autonym according to Ethnologue.

data/langdb.yaml

@@ -104,6 +104,7 @@ languages:
   btm: [Latn, [AS], Mandailing]
   bto: [Latn, [AS], Iriga Bicolano]
   bug: [Bugi, [AS], ᨅᨔ ᨕᨘᨁᨗ]
+  bum: [Latn, [AF], bulu]
   bxr: [Cyrl, [AS], буряад]
   byn: [Ethi, [AF], ብሊን]
   bzj: [Latn, [AM], Bileez Kriol]

data/language-data.json

@@ -655,6 +655,13 @@
             ],
             "ᨅᨔ ᨕᨘᨁᨗ"
         ],
+        "bum": [
+            "Latn",
+            [
+                "AF"
+            ],
+            "bulu"
+        ],
         "bxr": [
             "Cyrl",
             [
@@ -4960,6 +4967,7 @@
         "CM": [
             "fr",
             "en",
+            "bum",
             "ff",
             "bkm",
             "bas",