feature: added human-readable names for input keys

[unstoppablecarl]

This PR

• Adds a new feature

Describe the changes below:

Adds human readable strings for input keys.

import GetKeyName from Phaser.Input.Keyboard.GetKeyName
import KeyCodes from Phaser.Input.Keyboard.KeyCodes

GetKeyName(KeyCodes.LEFT) // '←' 
GetKeyName('LEFT') // '←'
GetKeyName(KeyCodes.BACKSPACE) // 'Backspace'
GetKeyName('BACKSPACE') // 'Backspace'
GetKeyName(KeyCodes.OPEN_BRACKET) // '['
GetKeyName('OPEN_BRACKET') // '['

This PR still needs tests and documentation updates. I'm happy to do them if this PR is approved.