Remove Travis CI in favour of GitHub Actions

Author: hugovk

.travis.yml

@@ -16,7 +16,7 @@ documentation. Some useful information:
 - We keep the master branch passing all tests at all times on all
   supported versions.
 
-`Travis CI <https://travis-ci.org/html5lib/html5lib-python/>`_ is run
+`GitHub Actions <https://github.com/html5lib/html5lib-python/actions>`_ is run
 against all pull requests and should enforce all of the above.
 
 We use `Opera Critic <https://critic.hoppipolla.co.uk/>`_ as an external

CONTRIBUTING.rst

@@ -1,9 +1,8 @@
 html5lib
 ========
 
-.. image:: https://travis-ci.org/html5lib/html5lib-python.svg?branch=master
-    :target: https://travis-ci.org/html5lib/html5lib-python
-
+.. image:: https://github.com/html5lib/html5lib-python/actions/workflows/python-tox.yml/badge.svg
+    :target: https://github.com/html5lib/html5lib-python/actions/workflows/python-tox.yml
 
 html5lib is a pure-python library for parsing HTML. It is designed to
 conform to the WHATWG HTML specification, as is implemented by all major