Add Reader options

[lthibault]

As part of Wetware, the need has arisen reimplement virtually every atom. Accordingly, I also need to adjust the map of predefined symbols to reflect my own implementation of Nil, and Bool.

This PR implements the Option type for reader.Reader. Currently, options exist to configure:

• the macro table
• the dispatch table
• predefined symbols

⏱️ Estimated review time: < 10 minutes ✅ Merge when ready