Initial library implementations and tests (#1)

- [x] Implements library according to instructions, with tests.
- [x] GitHub Actions workflow to lint and test library.

Reviewed-on: #1

.github/workflows/main.yaml

@@ -0,0 +1,29 @@
+name: Main Workflow
+on:
+  pull_request:
+    branches:
+      - main
+  push:
+    branches:
+      - main
+jobs:
+  lint-and-test:
+    name: Lint and test library
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Java
+        uses: actions/setup-java@v3
+        with:
+          distribution: 'adopt'
+          java-version: 17
+
+      - name: Verify Gradle wrapper
+        uses: gradle/wrapper-validation-action@v1
+
+      - name: Setup Gradle
+        uses: gradle/gradle-build-action@v2
+
+      - name: Run checks
+        run: ./gradlew check