Replace TravisCI with GitHub Actions. (#507)

- Resolves #506

.github/workflows/mvn-build.yml

@@ -0,0 +1,23 @@
+name: Maven build
+
+on:
+  pull_request:
+    branches: [main]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Set up Java
+        uses: actions/setup-java@v1
+        with:
+          java-version: '11'
+      - name: Build artifacts, javadocs, and site
+        run: |
+          mvn install -B -V
+          mvn javadoc:jar
+          mvn javadoc:test-aggregate
+          mvn site
+      - name: Upload coverage report to Codecov
+        run: bash <(curl -s https://codecov.io/bash)

README.md

@@ -1,6 +1,5 @@
 # The Archives Unleashed Toolkit
-[![Build Status](https://travis-ci.org/archivesunleashed/aut.svg?branch=master)](https://travis-ci.org/archivesunleashed/aut)
-[![codecov](https://codecov.io/gh/archivesunleashed/aut/branch/master/graph/badge.svg)](https://codecov.io/gh/archivesunleashed/aut)
+[![codecov](https://codecov.io/gh/archivesunleashed/aut/branch/main/graph/badge.svg)](https://codecov.io/gh/archivesunleashed/aut)
 [![Maven Central](https://maven-badges.herokuapp.com/maven-central/io.archivesunleashed/aut/badge.svg)](https://maven-badges.herokuapp.com/maven-central/io.archivesunleashed/aut)
 [![Javadoc](https://javadoc-badge.appspot.com/io.archivesunleashed/aut.svg?label=javadoc)](http://api.docs.archivesunleashed.io/0.70.0/apidocs/index.html)
 [![Scaladoc](https://javadoc-badge.appspot.com/io.archivesunleashed/aut.svg?label=scaladoc)](http://api.docs.archivesunleashed.io/0.70.0/scaladocs/index.html)