fix: correct link to docs (#5)

* fix: correct link to docs

* docs: update language around list of libraries

Author: busunkim96

README.rst

@@ -16,7 +16,7 @@ projects     programmatically.
 .. |versions| image:: https://img.shields.io/pypi/pyversions/google-cloud-billing.svg
    :target: https://pypi.org/project/google-cloud-billing/
 .. _Cloud Billing API: https://cloud.google.com/billing
-.. _Client Library Documentation: https://googleapis.dev/python/billing/latest
+.. _Client Library Documentation: https://googleapis.dev/python/cloudbilling/latest
 .. _Product Documentation:  https://cloud.google.com/billing
 
 Quick Start
@@ -76,8 +76,8 @@ Next Steps
    API to see other available methods on the client.
 -  Read the `Cloud Billing API Product documentation`_ to learn
    more about the product and see How-to Guides.
--  View this `repository’s main README`_ to see the full list of Cloud
+-  View this `README`_ to see the full list of Cloud
    APIs that we cover.
 
 .. _Cloud Billing API Product documentation:  https://cloud.google.com/billing
-.. _repository’s main README: https://github.com/googleapis/google-cloud-python/blob/master/README.rst
+.. _README: https://github.com/googleapis/google-cloud-python/blob/master/README.rst