Add extracted source directory and README navigation

extracted-source/node_modules/lodash-es/_mapToArray.js

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+/**
+ * Converts `map` to its key-value pairs.
+ *
+ * @private
+ * @param {Object} map The map to convert.
+ * @returns {Array} Returns the key-value pairs.
+ */
+function mapToArray(map) {
+  var index = -1,
+      result = Array(map.size);
+
+  map.forEach(function(value, key) {
+    result[++index] = [key, value];
+  });
+  return result;
+}
+
+export default mapToArray;