Add support for BLE HID keyboard

Nobody has claimed this yet.

**Describe the problem you have/What new integration you would like**

Implement a BLE HID Keyboard to send keystrokes to connected tablets or smartphones.

**Please describe your use case for this integration and alternatives you've tried:**

Use-case: Wall-mounted iPad which is used as a smart home (status) display which is supposed to be woken up by sending for example ESC key to wake it up from sleep. OR: control the global screenbrightness by sending keystrokes via BLE HID keyboard.
All this is not really possible from an app itself as iOS does not support this easily.

I have already done this with my quick and dirty Arduino sketch using an ESP32 and my iPad. It is working as expected, but I would like to see this in ESPHome too.

**Additional context**

Basically most of this code could be used: https://github.com/olegos76/nimble_kbdhid_example
It also works with the older ESP-IDF 3.3.4.

Start by reviewing the linked nimble_kbdhid_example and the existing Arduino sketch described in the issue, including its ESP-IDF 3.3.4 compatibility. Determine where ESPHome handles ESP32 Bluetooth integrations. Done means a configured BLE HID keyboard can send keystrokes such as ESC to connected tablets or smartphones.

Written by the indexing model from the issue text.