readme: update build status badge

Author: jcarpent

README.md

@@ -3,7 +3,7 @@ EigenPy — Efficient Python bindings between Numpy/Eigen
 
 <p align="center">
   <a href="https://opensource.org/licenses/BSD-2-Clause"><img src="https://img.shields.io/badge/License-BSD%202--Clause-green.svg" alt="License"/></a>
-  <a href="https://travis-ci.org/stack-of-tasks/eigenpy"><img src="https://travis-ci.org/stack-of-tasks/eigenpy.svg?branch=master" alt="Build Status"/></a>
+  <a href="https://github.com/stack-of-tasks/eigenpy/workflows/linux.yml"><img alt="Build Status" src="https://github.com/stack-of-tasks/eigenpy/actions/workflows/linux.yml/badge.svg?branch=devel" /></a>
   <a href="https://anaconda.org/conda-forge/eigenpy"><img src="https://img.shields.io/conda/dn/conda-forge/eigenpy.svg" alt="Conda Downloads"/></a>
   <a href="https://anaconda.org/conda-forge/eigenpy"><img src="https://img.shields.io/conda/vn/conda-forge/eigenpy.svg" alt="Conda Version"/></a>
   <a href="https://badge.fury.io/py/eigenpy"><img src="https://badge.fury.io/py/eigenpy.svg" alt="PyPI version"></a>