Move internal modules to “internal” folder.

.internal/baseLt.js

@@ -0,0 +1,14 @@
+/**
+ * The base implementation of `lt` which doesn't coerce arguments.
+ *
+ * @private
+ * @param {*} value The value to compare.
+ * @param {*} other The other value to compare.
+ * @returns {boolean} Returns `true` if `value` is less than `other`,
+ *  else `false`.
+ */
+function baseLt(value, other) {
+  return value < other;
+}
+
+export default baseLt;