feat: Allow nonrecursive whole-function dependencies (#2)

And implement negate on numbers, and use dependencies to define subtract.

Co-authored-by: Glen Whitney <glen@studioinfinity.org>
Reviewed-on: #2

number/all.mjs

@@ -0,0 +1,3 @@
+export {add} from './add.mjs'
+export {negate} from './negate.mjs'
+export {subtract} from '../generic/subtract.mjs'

number/negate.mjs

@@ -0,0 +1,3 @@
+export const negate = {
+   number: [[], n => -n]
+}