Move internal modules to “internal” folder.

.internal/isStrictComparable.js

@@ -0,0 +1,15 @@
+import isObject from './isObject.js';
+
+/**
+ * Checks if `value` is suitable for strict equality comparisons, i.e. `===`.
+ *
+ * @private
+ * @param {*} value The value to check.
+ * @returns {boolean} Returns `true` if `value` if suitable for strict
+ *  equality comparisons, else `false`.
+ */
+function isStrictComparable(value) {
+  return value === value && !isObject(value);
+}
+
+export default isStrictComparable;