Move internal modules to “internal” folder.

.internal/baseIndexOfWith.js

@@ -0,0 +1,23 @@
+/**
+ * This function is like `baseIndexOf` except that it accepts a comparator.
+ *
+ * @private
+ * @param {Array} array The array to inspect.
+ * @param {*} value The value to search for.
+ * @param {number} fromIndex The index to search from.
+ * @param {Function} comparator The comparator invoked per element.
+ * @returns {number} Returns the index of the matched value, else `-1`.
+ */
+function baseIndexOfWith(array, value, fromIndex, comparator) {
+  let index = fromIndex - 1;
+  const length = array.length;
+
+  while (++index < length) {
+    if (comparator(array[index], value)) {
+      return index;
+    }
+  }
+  return -1;
+}
+
+export default baseIndexOfWith;