added workflow for the master branch push and adjusted the badges (#41)

Author: AndrewSav

.github/workflows/master.yml

@@ -0,0 +1,19 @@
+name: all tests
+
+on:
+  push:
+    branches: master
+
+jobs:
+  # Run tests
+  test:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository and submodules
+        uses: actions/checkout@v2
+        with:
+          submodules: recursive
+
+      - name: Run all tests
+        run: make

README.md

@@ -13,11 +13,11 @@ Thank you very much.
 
 ### Build
 
-[![Build Status](https://travis-ci.com/mailserver2/mailserver.svg?branch=master)](https://travis-ci.com/mailserver2/mailserver)
+[![Build Status](https://github.com/mailserver2/mailserver/actions/workflows/master.yml/badge.svg)](https://github.com/mailserver2/mailserver/actions/workflows/master.yml)
 
 ### Docker image
 
-[![](https://images.microbadger.com/badges/image/mailserver2/mailserver:latest.svg)](https://microbadger.com/images/mailserver2/mailserver:latest) [![](https://img.shields.io/docker/automated/mailserver2/mailserver.svg)](https://hub.docker.com/r/mailserver2/mailserver/builds/) [![](https://img.shields.io/docker/pulls/mailserver2/mailserver.svg)](https://hub.docker.com/r/mailserver2/mailserver/) [![](https://img.shields.io/docker/stars/mailserver2/mailserver.svg)](https://hub.docker.com/r/mailserver2/mailserver/) [![](https://img.shields.io/badge/bitcoin-donate-green.svg)](https://keybase.io/hardware)
+[![](https://images.microbadger.com/badges/image/mailserver2/mailserver:latest.svg)](https://microbadger.com/images/mailserver2/mailserver:latest) [![](https://img.shields.io/docker/automated/mailserver2/mailserver.svg)](https://hub.docker.com/r/mailserver2/mailserver/builds/) [![](https://img.shields.io/docker/pulls/mailserver2/mailserver.svg)](https://hub.docker.com/r/mailserver2/mailserver/) [![](https://img.shields.io/docker/stars/mailserver2/mailserver.svg)](https://hub.docker.com/r/mailserver2/mailserver/)
 
 **mailserver2/mailserver** is a simple and full-featured mail server build as a set of multiple docker images, including: