✨ Convert double to Number implicitly

[SizzinSeal]

Overview

title

Motivation

Consider the following:

Number num = double(2);

This code does not compile, even though it really should

Implementation

Number is defined manually instead of through macros, so the constructor is not marked explicit

[sufferiing]

If we want to have Number have some special behavior, I think it might be better to define it manually rather than through the NEW_UNIT macro. I would like to try to keep these macros from getting any more complex.