Update README.md (#147)

- In this commit, I have updated the docs to use the new method of presenting the Intercom messenger
- This change follows he deprecated functions table here https://github.com/intercom/intercom-react-native/releases#:~:text=displayMessenger,present released in v6.0.0

Co-authored-by: Brian Boyle <[email protected]>

Author: mitchiemt11

README.md

@@ -613,7 +613,7 @@ Handles the opening of an Intercom push message. This will retrieve the URI from
 `Promise<boolean>`
 ___
 
-### `Intercom.displayMessenger()`
+### `Intercom.present()`
 
 Opens the Intercom Messenger automatically to the best place for your users.