Feature Request: LWIP ALTCP support

### Basic Infos

- [x] This issue complies with the [issue POLICY doc](https://github.com/esp8266/Arduino/blob/master/POLICY.md).
- [x] I have read the documentation at [readthedocs](https://arduino-esp8266.readthedocs.io/en/latest) and the issue is not addressed there.
- [x] I have tested that the issue is present in current master branch (aka latest git).
- [x] I have searched the issue tracker for a similar issue.
- [x] If there is a stack dump, I have decoded it.
- [ ] I have filled out all fields below.

#### Platform

- Hardware: [INDEPENDENT]
- Core Version: [ALL]
- Development Env: [Platformio]
- Operating System: [Windows]

### Problem Description

I'm maintaining a [H4AsyncTCP](https://github.com/HamzaHajeir/H4AsyncTCP) library after the passage of its author a year ago, and I'm heading to develop TLS by utilizing [LwIP ALTCP](https://www.nongnu.org/lwip/2_1_x/group__altcp__api.html) raw APIs, which offers seamless shift out from raw TCP APIs code with the help of ALTCP TLS.

However, observed that ALTCP headers are not present within lwip library.

How would esp8266 arduino team observe this request?
What can someone proceed with ALTCP & using Arduino altogether?

With thanks,
Hamza Hajeir