Document how to use source map support

This provider doesn't translate error stack traces using source maps. We should document how you can set that up yourself, by installing `source-map-support` and adding `source-map-support/register` to AVA's `require` configuration.

Start by locating the repository's usage documentation and examples of AVA's require configuration. Document installing `source-map-support`, adding `source-map-support/register` to that configuration, and verify that the instructions clearly explain how users can enable source-map support themselves.

Written by the indexing model from the issue text.