feat: Start arithmetic functions for complex

So far, adds absquare and add. To get these working, especially on mixed
  types of arguments, this also adds some additional features:
  * Allows conversions to generic types, with the matched type
    determined from the return value of the built convertor
  * Adds predicate-based type patterns
  * Adds conversion from any non-complex type T to Complex(T)
  * Starts tests for complex arithmetic

src/generic/relational.js

@@ -18,7 +18,7 @@ export const equal = match([Any, Any], (math, [T, U]) => {
       return boolnum(() => false)(math)
    }
    // Get the type of the first argument to the matching checker:
-   const ByType = matched(exactChecker.template).flat()[0]
+   const ByType = matched(exactChecker.template, math).flat()[0]
    // Now see if there are tolerances for that type:
    const typeConfig = math.resolve('config', [ByType])
    if ('relTol' in typeConfig) {