rn,flags: add feature flag to show/hide the 'Raise Hand' button

react/features/base/flags/constants.js

  */
 export const PIP_ENABLED = 'pip.enabled';
 
+/**
+ * Flag indicating if raise hand feature should be enabled.
+ * Default: enabled.
+ */
+export const RAISE_HAND_ENABLED = 'raise-hand.enabled';
+
 /**
  * Flag indicating if recording should be enabled.
  * Default: auto-detected.

react/features/toolbox/components/native/RaiseHandButton.js

 import { connect } from '../../../base/redux';
 import { AbstractButton } from '../../../base/toolbox';
 import type { AbstractButtonProps } from '../../../base/toolbox';
+import { RAISE_HAND_ENABLED, getFeatureFlag } from '../../../base/flags';
 
 /**
  * The type of the React {@code Component} props of {@link RaiseHandButton}.
  * Maps part of the Redux state to the props of this component.
  *
  * @param {Object} state - The Redux state.
+ * @param {Object} ownProps - The properties explicitly passed to the component instance.
  * @private
- * @returns {{
- *     _raisedHand: boolean
- * }}
+ * @returns {Props}
  */
-function _mapStateToProps(state): Object {
+function _mapStateToProps(state, ownProps): Object {
     const _localParticipant = getLocalParticipant(state);
+    const enabled = getFeatureFlag(state, RAISE_HAND_ENABLED, true);
+    const { visible = enabled } = ownProps;
 
     return {
         _localParticipant,
-        _raisedHand: _localParticipant.raisedHand
+        _raisedHand: _localParticipant.raisedHand,
+        visible
     };
 }