Lua Parsing

Would you be open to accepting a PR to support a Lua parsing?
This way some more custom log formats can be added without having to recompile, or add into source.

No files, tests, or parser entry points are named. Start by locating the existing log-format parsing path and how formats are registered; determine where Lua support would integrate without recompilation or source changes. Done means custom log formats can be added through Lua and the existing parsing behavior remains covered by tests.

Written by the indexing model from the issue text.