Update README.md

[carnevalle]

Description

One Line Summary

Lowercase composer require. "OneSignal/onesignal-php-api" to "onesignal/onesignal-php-api"

Details

Motivation

This fixes a bug with composer.

require.OneSignal/onesignal-php-api is invalid, it should not contain upper  
  case characters. Please use onesignal/onesignal-php-api instead.

Testing

Manual testing

Ran composer update and it worked :-)

Checklist

Overview

• [x] I have filled out all REQUIRED sections above
• [x] PR does one thing
  • If it is hard to explain how any codes changes are related to each other then it most likely needs to be more than one PR
• [x] Any Public API changes are explained in the PR details and conform to existing APIs

Testing

• [x] I have personally tested this on my device, or explained why that is not possible

Final pass

• [x] Code is as readable as possible.
  • Simplify with less code, followed by splitting up code into well named functions and variables, followed by adding comments to the code.
• [x] I have reviewed this PR myself, ensuring it meets each checklist item
  • WIP (Work In Progress) is ok, but explain what is still in progress and what you would like feedback on. Start the PR title with "WIP" to indicate this.

[iAmWillShepherd]

👋🏽 @carnevalle

Thanks so much for your contribution 🎉 A member of our SDK team should get to this soon and hopefully get it merged! If we have any questions or requests, we'll @-mention you here 🙏🏽

[nan-li]

Hey @carnevalle thank you so much for catching this.