Update project to track the nginx.org GitHub repo

[jputrino]

Is your feature request related to a problem? Please describe

The source for nginx.org recently moved from Mercurial to GitHub. We need to update this project accordingly so we can continue to pick up updates as they're made.

Describe the solution you'd like

• use https://github.com/nginx/nginx.org instead of http://hg.nginx.org/nginx.org
• make the version field be a link to the upstream commit, like https://github.com/nginx/nginx.org/commit/7010720ef8c1b9dedadf8befb7b8090bdefc62cd

Describe alternatives you've considered

Additional context