Update built_with.rst (#5887)

Salted is a very fast link checker for multiple file formats. It can be used as a library and through the command line. Salted reaches its speed by using asynchronous requests with aiohttp.

docs/built_with.rst

@@ -27,3 +27,4 @@ project, pointing to `<https://github.com/aio-libs/aiohttp>`_.
 * `Mariner <https://gitlab.com/radek-sprta/mariner>`_ Command-line torrent searcher.
 * `DEEPaaS API <https://github.com/indigo-dc/DEEPaaS>`_ REST API for Machine learning, Deep learning and artificial intelligence applications.
 * `BentoML <https://github.com/bentoml/BentoML>`_ Machine Learning model serving framework
+* `salted <https://github.com/RuedigerVoigt/salted>`_ fast link check library (for HTML, Markdown, LaTeX, ...) with CLI