feat: implement Simple List API for S3 objects

- Add List method with ListInput and ListResponse structs following simples3 patterns
- Implement pagination, prefix filtering, and delimiter grouping
- Add comprehensive test suite for List functionality
- Update tests to use environment variables instead of hardcoded values
- Fix deprecated io/ioutil usage throughout codebase
- Add comprehensive README with API documentation and examples
- Add Nix development environment with flake.nix
- Add Justfile for modern command runner
- Add Docker Compose setup for local MinIO testing
- Update GitHub Actions to use Nix and Justfile for CI consistency
- Fix test naming and setup flow issues

New API:
s3.List(ListInput{
    Bucket: "my-bucket",
    Prefix: "documents/",
    MaxKeys: 100,
})

All tests pass with new simplified API design.

.github/workflows/go-test.yml

@@ -10,31 +10,19 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+      - name: Checkout code
+        uses: actions/checkout@v4
 
-    - name: Set up Go
-      uses: actions/setup-go@v2
-      with:
-        go-version: 1.15
-    - name: Setup minio
-      run: |
-          docker run -d -p 9000:9000 --name minio \
-                     -e "MINIO_ACCESS_KEY=minioadmin" \
-                     -e "MINIO_SECRET_KEY=minioadmin" \
-                     -v /tmp/data:/data \
-                     -v /tmp/config:/root/.minio \
-                     minio/minio server /data
-                     
-          export AWS_ACCESS_KEY_ID=minioadmin
-          export AWS_SECRET_ACCESS_KEY=minioadmin
-          export AWS_EC2_METADATA_DISABLED=true
-          
-          aws --endpoint-url http://127.0.0.1:9000/ s3 mb s3://testbucket
-           
-    - name: Run Go Test
-      run: go test -v ./...
-      env:
-        AWS_S3_BUCKET: testbucket 
-        AWS_S3_ACCESS_KEY: minioadmin
-        AWS_S3_SECRET_KEY: minioadmin
-        AWS_S3_ENDPOINT: http://127.0.0.1:9000
+      - name: Install Nix
+        uses: cachix/install-nix-action@v27
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable
+
+      - name: Run Tests via Justfile
+        env:
+          AWS_S3_BUCKET: testbucket
+          AWS_ACCESS_KEY_ID: minioadmin
+          AWS_SECRET_ACCESS_KEY: minioadmin
+          AWS_S3_ENDPOINT: http://127.0.0.1:9000
+          AWS_EC2_METADATA_DISABLED: "true"
+        run: nix develop --command just test-local