Function called when a reaction is selected in the message overlay, this is called on both the add and remove action.
This function does not override the default behavior of the reaction being selected.
Please refer to [the guide on customizing message actions](../../../../guides/message_actions_customization.mdx) for details.

| Type |
| - |
| function |

| Parameter | Description |
| - | - |
| message | message the action is called on |
| reactionType | string designating the type of reaction |