Function to upload an attached file in `MessageInput`. This function adds a file to [`fileUploads`](../../../contexts/message_input_context.mdx#fileuploads) array and calls `channel.sendFile`.
This function takes a file from [react-native-document-picker](https://www.npmjs.com/package/react-native-document-picker) as parameter.

| Type |
| - |
| `(file) => Promise` |