Add an index or make benchmarks searchable

Thanks for this great tool!

We're using it in [the Qi project](https://drym-org.github.io/qi/benchmarks/) to track changes in a large number of benchmarks over time, as a sanity check and for forensic purposes.

As there are many tracked benchmarks, it would be useful to have a simple index of benchmarks, say, at the top of the page or in a sidebar or dropdown, to be able to jump directly to a specific benchmark. Otherwise, being able to just search the page using the browser's search feature for the name of the benchmark would also help (the benchmark names don't seem to register as searchable text from the browser's perspective). The former would be preferable since it would hopefully allow the individual benchmarks to be linkable and they could be directly linked in docs, discussions, or anywhere else. But if both could be addressed, that would be ideal.