Add node modules and new code for release (#57)

Co-authored-by: taakleton <taakleton@users.noreply.github.com>

node_modules/underscore/modules/isBoolean.js

@@ -0,0 +1,6 @@
+import { toString } from './_setup.js';
+
+// Is a given value a boolean?
+export default function isBoolean(obj) {
+  return obj === true || obj === false || toString.call(obj) === '[object Boolean]';
+}