Merge pull request #2808 from purificant/ci_badge

replace travis badge with github actions badge

README.md

@@ -1,6 +1,6 @@
 # Natural Language Toolkit (NLTK)
 [![PyPI](https://img.shields.io/pypi/v/nltk.svg)](https://pypi.python.org/pypi/nltk)
-[![Travis](https://travis-ci.org/nltk/nltk.svg?branch=develop)](https://travis-ci.org/nltk/nltk)
+![CI](https://github.com/nltk/nltk/actions/workflows/ci.yaml/badge.svg?branch=develop)
 
 NLTK -- the Natural Language Toolkit -- is a suite of open source Python
 modules, data sets, and tutorials supporting research and development in Natural