Add sitemap generator

[hungmi]

This PR adds sitemap_generator and add some links mentioned in #40.

I also add /developers/new & /businesses/new since they are part of sign up process. I can remove them If that is not needed.

I have tested it locally and the sitemap.xml seems to be ok.
But I don't know how to write test for it 😅. Does anyone have any suggestion?

And the next step is set rake "-s sitemap:refresh"(according to the doc) on Heroku scheduler.

Pull request checklist

• Your code contains tests relevant for code you modified
• You have linted and tested the project with bin/check

[joemasilotti]

Thanks for kicking this off! I made a few small change requests, other than that it looks good.

We will have to host the sitemap somewhere else, like S3, as Heroku doesn't have persistent storage. But I can take care of that.

[joemasilotti]

I'm fine with a single smoke test if it doesn't take too long. Running the command and verifying that the XML file is created without any raised errors should be good enough!

[hungmi]

I have added a test to run rails sitemap:refresh:no_ping.
But I can't find a way to add -s when I invoke it, so I followed this open issue to prevent unneccessarily outputs.
Thanks for your review!

[joemasilotti]

This is looking great. I'm just figuring out the S3 hosting and will merge in.

[joemasilotti]

OK, I think we're good! Turned out I need to add a bunch of stuff to get the S3 upload working and Google Search Console pointing to the sitemap correctly. I'm going to document all of the non-code stuff on the Wiki soon.

Thanks again for the PR!

[joemasilotti]

And we're good! Thanks again 🎉