EventIndex: Hide the feature behind a labs flag.

src/settings/Settings.js

@@ -120,6 +120,12 @@ export const SETTINGS = {
         supportedLevels: LEVELS_FEATURE,
         default: false,
     },
+    "feature_event_indexing": {
+        isFeature: true,
+        supportedLevels: LEVELS_DEVICE_ONLY_SETTINGS,
+        displayName: _td("Enable local event indexing and E2EE search (requires restart)"),
+        default: false,
+    },
     "useCiderComposer": {
         displayName: _td("Use the new, faster, composer for writing messages"),
         supportedLevels: LEVELS_ACCOUNT_SETTINGS,