Add user_guest_status_changed event

- Add new event user_guest_status_changed with users:read scope for Events API

Author: Slack API Ref Buildbot

docs.slack.dev/events/events.json

@@ -1497,6 +1497,16 @@
       "RTM"
     ]
   },
+  {
+    "name": "user_guest_status_changed",
+    "description": "A user's guest status changed.",
+    "scopes": [
+      "users:read"
+    ],
+    "APIs": [
+      "Events"
+    ]
+  },
   {
     "name": "user_huddle_changed",
     "description": "A user's huddle status has changed",

events/user_guest_status_changed.json

@@ -0,0 +1,10 @@
+{
+  "name": "user_guest_status_changed",
+  "desc": "A user's guest status changed..",
+  "scopes": [
+    "users:read"
+  ],
+  "APIs": [
+    "Events"
+  ]
+}