Add extracted source directory and README navigation

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

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+import copyObject from './_copyObject.js';
+import getSymbolsIn from './_getSymbolsIn.js';
+
+/**
+ * Copies own and inherited symbols of `source` to `object`.
+ *
+ * @private
+ * @param {Object} source The object to copy symbols from.
+ * @param {Object} [object={}] The object to copy symbols to.
+ * @returns {Object} Returns `object`.
+ */
+function copySymbolsIn(source, object) {
+  return copyObject(source, getSymbolsIn(source), object);
+}
+
+export default copySymbolsIn;