feat: Add and illustrate multiple ways of specifying implementations (#19)

Resolves #9.

Co-authored-by: Glen Whitney <glen@studioinfinity.org>
Reviewed-on: #19

src/number/add.mjs

@@ -1,5 +1,5 @@
 export {Types} from './Types/number.mjs'
 
 export const add = {
-   '...number': [[], addends => addends.reduce((x,y) => x+y, 0)],
+   '...number': addends => addends.reduce((x,y) => x+y, 0),
 }