ESP32-BLE-Keyboard v0.3.0

Changelog:

• Fix: Reduce the max. device/manufacturer name length to fix compatibility issues with Apple devices (Thanks to @sivar2311 for implementing this in PR #111)
• Fix: Added a default delay of 8 milliseconds between each key event in order to compensate for slow applications that can't properly handle fast input (Thanks to @sivar2311 for implementing this in PR #111)
• Feature: Added a setDelay method to set the delay mentioned above to a custom value (Thanks to @sivar2311 for implementing this in PR #111)
• Fix: Reduce memory footprint (meaning you can use WiFi and BLE together now) (Thanks to @sivar2311 for implementing this in PR #111)
• Feature: Added support for NimBLE to further reduce the memory footprint (Thanks to @sivar2311 for implementing this in PR #111)
• Fix: Start advertising on disconnect again to ensure the device will show up on again on Apple devices (Thanks to @aovestdipaperino and @sivar2311 for implementing this in PR #86 and PR #111)
• Refactor: Everything is implemented in the BleKeyboard class now. KeyboardOutputCallbacks and BleConnectionStatus are not necessary anymore and have been removed.
• Feature: added setName function to allow changing the name of the device using a stored preference (must be called before begin) (Thanks to @millst for implementing this in PR #100)
• Docs: Added documentation and information on NimBLE to the Readme (Thanks to @sivar2311 for implementing this in PR #111)