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/nanomath.js

@@ -5,6 +5,14 @@ import * as numbers from './number/all.js'
 import * as complex from './complex/all.js'
 import {TypeDispatcher} from '#core/TypeDispatcher.js'
 
-const math = new TypeDispatcher(booleans, coretypes, generics, numbers, complex)
+// At the moment, since we are not sorting patterns in any way,
+// order matters in the construction. Patterns that come later in
+// the following list will be tried earlier. (The rationale for that
+// ordering is that any time you merge something, it should supersede
+// whatever has been merged before.)
+// Hence, in building the math instance, we put complex first because
+// we want its conversion (which converts _any_ non-complex type to
+// complex, potentially making a poor overload choice) to be tried last.
+const math = new TypeDispatcher(complex, generics, booleans, coretypes, numbers)
 
 export default math