Summary:Thanks for submitting a pull request! Please provide enough information so that others can review your pull request:
(You can skip this if you're fixing a typo or adding an app to the Showcase.)
Explain the **motivation** for making this change. What existing problem does the pull request solve?
it wasn't clear how to use various methods such as mergeItem, multiMerge, etc, so after figuring it out I thought it would be useful to provide clear examples for others.
Example: When "Adding a function to do X", explain why it is necessary to have a way to do X.
**Test plan (required)**
Demonstrate the code is solid. Example: The exact commands you ran and their output, screenshots / videos if the pull request changes UI.
Make sure tests pass on both Travis and Circle CI.
**Code formatting**
See the simple [style guide](https://github.com/facebook/react-native/blob/master/CONTRIBUTING.md#style-guide).
…Set, multiGet, and multiRemove
Closes https://github.com/facebook/react-native/pull/6423
Differential Revision: D3048502
Pulled By: vjeux
fb-gh-sync-id: dfe13c6a88fa9d3e7646b5ecaa5f594bfaba8271
shipit-source-id: dfe13c6a88fa9d3e7646b5ecaa5f594bfaba8271
afffcde15c