switch badges to github actions

cargo badges does not support github actions yet:
https://github.com/rust-lang/crates.io/pull/1838

README.md

@@ -2,7 +2,7 @@
 
 [![Crates.io](https://img.shields.io/crates/v/ncspot.svg)](https://crates.io/crates/ncspot)
 [![Gitter](https://badges.gitter.im/ncspot/community.svg)](https://gitter.im/ncspot/community?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge)
-[![Build Status](https://travis-ci.com/hrkfdn/ncspot.svg?token=DoBH2xZ13CfuTfqgEyp7&branch=master)](https://travis-ci.com/hrkfdn/ncspot)
+[![Build](https://github.com/hrkfdn/ncspot/workflows/Build/badge.svg)](https://github.com/hrkfdn/ncspot/actions?query=workflow%3ABuild)
 [![Snap Status](https://build.snapcraft.io/badge/popey/ncspot-snap.svg)](https://build.snapcraft.io/user/popey/ncspot-snap)
 
 [![Packaging status](https://repology.org/badge/vertical-allrepos/ncspot.svg)](https://repology.org/project/ncspot/versions)