Added sitemap.xml gen

[forrest321]

Added sitemap.xml gen

[googlebot]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project (if not, look below for help). Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

📝 Please visit https://cla.developers.google.com/ to sign.

Once you've signed (or fixed any issues), please reply here (e.g. I signed it!) and we'll verify it.

---

What to do if you already signed the CLA

Individual signers

• It's possible we don't have your GitHub username or you're using a different email address on your commit. Check your existing CLA data and verify that your email is set on your git commits.

Corporate signers

• Your company has a Point of Contact who decides which employees are authorized to participate. Ask your POC to be added to the group of authorized contributors. If you don't know who your Point of Contact is, direct the Google project maintainer to go/cla#troubleshoot (Public version).
• The email used to register you as an authorized contributor must be the email used for the Git commit. Check your existing CLA data and verify that your email is set on your git commits.
• The email used to register you as an authorized contributor must also be attached to your GitHub account.

[forrest321]

I signed it!

[forrest321]

I signed it!

[googlebot]

CLAs look good, thanks!

[ebidel]

Is there a node lib we could use instead of manually crafting the xml?

[ebidel]

Use let throughout

[abdonrd]

Interested in this!

[forrest321]

Requested changed are done.

[forrest321]

This one fell off my radar, thought I'd get it done. Hope that helps.

[Kiina]

Just a note, the sitemap generator might need a filter for anchor same page links (aka example.com/#home). I'm kinda sure they shouldn't be included in a sitemap in basically any case but they get included in the current implementation.

My quick and dirty fix would be to just add page.url = page.url.replace(/#.*$/,''); before the if (crawledPages.has(page.url)) { so it removed the anchors but i'm not sure how that interferes with the original crawl function when people wanna build the graph