[update] CI's badge and [update] CHANGELOG.md

CHANGELOG.md

@@ -23,6 +23,7 @@ This is the Changelog for the vim-airline project.
   - coc extensions can also show additional status messages
   - [coc-git](https://github.com/neoclide/coc-git) extension integrated into hunks extension
 - Other
+  - Changed CI from travis-ci.org to GitHub Actions
   - Introduce Vim script static analysis using [reviewdog](https://github.com/reviewdog/action-vint)
   - Added multiple Vim versions to unit tests using Travis CI
   - Added option to show short paths in the status line

README.md

@@ -1,4 +1,8 @@
-# vim-airline [![Build Status](https://travis-ci.org/vim-airline/vim-airline.svg?branch=master)](https://travis-ci.org/vim-airline/vim-airline) [![Say Thanks!](https://img.shields.io/badge/Say%20Thanks-!-1EAEDB.svg)](https://saythanks.io/to/cb%40256bit.org) [![reviewdog](https://github.com/vim-airline/vim-airline/workflows/reviewdog/badge.svg?branch=master&event=push)](https://github.com/vim-airline/vim-airline/actions?query=workflow%3Areviewdog+event%3Apush+branch%3Amaster)
+# vim-airline 
+
+[![Say Thanks!](https://img.shields.io/badge/Say%20Thanks-!-1EAEDB.svg)](https://saythanks.io/to/cb%40256bit.org)
+[![reviewdog](https://github.com/vim-airline/vim-airline/workflows/reviewdog/badge.svg?branch=master&event=push)](https://github.com/vim-airline/vim-airline/actions?query=workflow%3Areviewdog+event%3Apush+branch%3Amaster)
+[![CI](https://github.com/vim-airline/vim-airline/workflows/CI/badge.svg)](https://github.com/vim-airline/vim-airline/actions?query=workflow%3ACI)
 
 Lean & mean status/tabline for vim that's light as air.