Add a reference to the URL display guidelines docs
Add a reference to the URL display guidelines docs

This adds a sentence with a link to the URL display guidelines [1] now that they are publicly available. I think this is useful context for how/why to use trickuri.

[1] https://chromium.googlesource.com/chromium/src/+/master/docs/security/url_display_guidelines/url_display_guidelines.md
chromium/trickuri,chromium/trickuri