Added link to benchmarks

Make sure there's always an easy to find link. #338.

README.md

@@ -2,6 +2,7 @@
 
 [![Go Report Card](https://goreportcard.com/badge/github.com/transparency-dev/trillian-tessera)](https://goreportcard.com/report/github.com/transparency-dev/trillian-tessera)
 [![OpenSSF Scorecard](https://api.scorecard.dev/projects/github.com/transparency-dev/trillian-tessera/badge)](https://scorecard.dev/viewer/?uri=github.com/transparency-dev/trillian-tessera)
+[![Benchmarks](https://img.shields.io/badge/Benchmarks-blue.svg)](https://transparency-dev.github.io/trillian-tessera/dev/bench/)
 [![Slack Status](https://img.shields.io/badge/Slack-Chat-blue.svg)](https://transparency-dev.slack.com/)
 
 Trillian Tessera is a Go library for building [tile-based transparency logs (tlogs)](https://c2sp.org/tlog-tiles).