update documentation link

Author: craigbarratt

docs/useful_links.rst

@@ -1,7 +1,7 @@
 Useful Links
 ============
 
--  `Documentation <https://github.com/custom-components/pyscript/blob/master/README.md>`__
+-  `Documentation <https://hacs-pyscript.readthedocs.io/en/latest>`__
 -  `Issues <https://github.com/custom-components/pyscript/issues>`__
 -  `Wiki <https://github.com/custom-components/pyscript/wiki>`__
 -  `GitHub repository <https://github.com/custom-components/pyscript>`__