feat: config and approximate equality

Establishes a global config object for a TypeDispatcher instance, so far
  with just properties representing comparison tolerances. Begins a
  "relational" group of functions with basic approximate equality, and
  an initial primitive ordering comparison. Ensures that methods that
  depend on properties of `config` will be properly updated when those
  properties change.

src/generic/config.js

@@ -0,0 +1,5 @@
+import {ImplementationsGenerator, onType} from '#core/helpers.js'
+import {Passthru} from '#core/TypePatterns.js'
+
+export const config = new ImplementationsGenerator(
+    () => onType(Passthru, {relTol: 1e-12, absTol: 1e-15}))