import org.gradle.api.tasks.PathSensitivity;
import org.gradle.api.tasks.TaskAction;
import org.gradle.internal.UncheckedException;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.nio.file.Files;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;

        appendFileContentsTo(document.head(), "<style>", releaseNotesCss, "</style>");
    }

    private void appendFileContentsTo(Element element, String open, File file, String close) {
        try (FileReader reader = new FileReader(file)) {
            element.append(open + CharStreams.toString(reader) + close);
        } catch (IOException e) {
            throw UncheckedException.throwAsUncheckedException(e);
        }
    }