Add support for http2 directive

[HLFH]

Changes with nginx 1.25.1                                        13 Jun 2023

    *) Feature: the "http2" directive, which enables HTTP/2 on a per-server
       basis; the "http2" parameter of the "listen" directive is now
       deprecated.

    *) Change: HTTP/2 server push support has been removed.

    *) Change: the deprecated "ssl" directive is not supported anymore.

    *) Bugfix: in HTTP/3 when using OpenSSL.


Changes with nginx 1.25.0                                        23 May 2023

    *) Feature: experimental HTTP/3 support.

Would be great to do syntax highlighting for the http2 directive.