Render time support?

Has anyone added or know how to add rendering time output for templates? I have some slow pages and it would be a huge benefit to see something like:

```

```

in the page source. It would allow me to narrow down view performance issues to a specific template very quickly.

The issue names no files or tests. Start by locating ego's template-rendering entry point and determine where template output can be timed; done means generated page source includes the template name and elapsed milliseconds while preserving normal rendering.

Written by the indexing model from the issue text.