Add news item about Sigstore Trust Root

Author: joshuagl

content/news.md

@@ -4,6 +4,14 @@ title: News
 
 > The [press](/press) page contains a full listing of news coverage.
 
+**June 16, 2021**
+
+The Sigstore community live-streams [key generation and signing ceremony
+](https://www.cncf.io/blog/2021/06/16/a-new-kind-of-trust-root/) for the
+Sigstore trust root, which is using The Update Framework (TUF) primitives to
+provide a PKI model with no single entity in charge of the trust root, and
+shorter root key lifespan than traditional PKI models.
+
 **March 5, 2021**
 
 The [TUF specification](https://theupdateframework.github.io/specification/latest/index.html)