Parse `rg` output.

[This function](https://github.com/KarlHeitmann/rg_wrapper/blob/8178db2cba9cfbb9141bb06887918004f859b40a/src/io.rs#L4) runs `rg` command, and currently it's output is being printed to STDOUT.

Take the output data from `rg` command and parse it. I did something similar on this other project called [chuletas_cleanup_warning](https://github.com/KarlHeitmann/chuletas_warning_hook), a hook for git. I think there may be a better way to do it, but you can have some inspiration by looking at this code (or better understand what I want to do in this project).

Start with the function in src/io.rs at the linked line and inspect how it currently runs rg and prints its output. Review the linked chuletas_warning_hook project for the intended parsing approach, then determine the parsed result this wrapper should expose and verify that rg output is no longer sent directly to STDOUT.

Written by the indexing model from the issue text.