Add NGF to the nginx.org homepage

[sindhushiv]

In the 'Other Projects' section on https://nginx.org/, we need to include links to the NGF docs and code.

The required changes should be made in this XML file: https://github.com/nginx/nginx.org/blob/main/xml/homepage.xml#L50

Docs link: https://docs.nginx.com/nginx-gateway-fabric/
Code link: https://github.com/nginxinc/nginx-gateway-fabric

[sjberman]

nginx/nginx.org#107

Will also update our own docs to use the proper logo.