Document SCIM feature flag in the README

README.md

@@ -323,6 +323,7 @@ Grist can be configured in many ways. Here are the main environment variables it
 | GRIST_SNAPSHOT_TIME_CAP            | optional. Define the caps for tracking buckets. Usage: {"hour": 25, "day": 32, "isoWeek": 12, "month": 96, "year": 1000}                                                                                                                                                                                                                                      |
 | GRIST_SNAPSHOT_KEEP                | optional. Number of recent snapshots to retain unconditionally for a document, regardless of when they were made                                                                                                                                                                                                                                              |
 | GRIST_PROMCLIENT_PORT              | optional. If set, serve the Prometheus metrics on the specified port number. ⚠️ Be sure to use a port which is not publicly exposed ⚠️.                                                                                                                                                                                                                         |
+| GRIST_ENABLE_SCIM                  | optional. If set, enable the [SCIM API Endpoint](https://support.getgrist.com/install/scim/) (experimental)                                                                                                                                                                                                                                                   |
 
 #### AI Formula Assistant related variables (all optional):