esp_netif_init() returns standard esp_err_t error code (unlike tcpip_adapter init), so shall be checked for the return value
Also to make the initialization code more consistent.
Intention is to partition the demo into multiple files, so that the
main program is quite easy to follow.
1. connectlib.c: For any URL parsing and TCP connection related stuff
2. sh2lib.c: Convenience functions for HTTP2+TLS. The goal here is to
expose a simpler API than nghttp2. If most usecases end up being
served with this library, it could potentially be moved into a separate
component
