Add ITIN to cspell dictionary

ITIN (Individual Taxpayer Identification Number) is used in the bank account docs but was not in the spell-check word list.

Co-authored-by: Stephanie Elliott <stephanieelliott@users.noreply.github.com>

Author: MelvinBot

cspell.json

@@ -163,6 +163,7 @@
         "IHDR",
         "INTECOMS",
         "IPHONEOS",
+        "ITIN",
         "ITSM",
         "Idology",
         "Inactives",