Update README + switch to GitHub actions

.github/workflows/build.yaml

@@ -0,0 +1,31 @@
+name: Java CI
+
+on:
+  push:
+    paths-ignore:
+      - '*.md'
+      - '**/*.md'
+    branches:
+      - '*'
+    tags:
+      - '*'
+  pull_request:
+    branches:
+      - master
+
+jobs:
+  build:
+    runs-on: ubuntu-24.04
+
+    steps:
+      - uses: actions/checkout@v3
+      - name: Set up JDK 17
+        uses: actions/setup-java@v3
+        with:
+          java-version: '17'
+          distribution: 'temurin'
+          cache: 'maven'
+      - name: Change JDK version in toolchain to old notation
+        run: sed -i 's/>17</>1.17</' ~/.m2/toolchains.xml
+      - name: Build with Maven
+        run: mvn --batch-mode --update-snapshots package