upgraded dependencies

vendor/symfony/string/README.md

@@ -0,0 +1,14 @@
+String Component
+================
+
+The String component provides an object-oriented API to strings and deals
+with bytes, UTF-8 code points and grapheme clusters in a unified way.
+
+Resources
+---------
+
+ * [Documentation](https://symfony.com/doc/current/components/string.html)
+ * [Contributing](https://symfony.com/doc/current/contributing/index.html)
+ * [Report issues](https://github.com/symfony/symfony/issues) and
+   [send Pull Requests](https://github.com/symfony/symfony/pulls)
+   in the [main Symfony repository](https://github.com/symfony/symfony)