lexicon: add pronouns field to actor profile

lexicons/actor/profile.json

···
             "maxGraphemes": 40,
             "maxLength": 400
           },
+          "pronouns": {
+            "type": "string",
+            "description": "Free-form preferred pronouns text.",
+            "maxGraphemes": 40,
+            "maxLength": 400
+          },
           "pinnedRepositories": {
             "type": "array",
             "description": "Any ATURI, it is up to appviews to validate these fields.",