code: function render(source, destination) {
    const unique = crypto.createHmac('sha1', PLUGIN_NAME).update(source).digest('hex');
    const mmdcExecutable = which.sync('mmdc');
    const mmdPath = path.join(destination, `${unique}.mmd`);
    const svgFilename = `${unique}.svg`;
    const svgPath = path.join(destination, svgFilename);
  
    // Write temporary file
    fs.outputFileSync(mmdPath, source);
  
    // Invoke mermaid.cli
    execSync(`${mmdcExecutable} -i ${mmdPath} -o ${svgPath} -b transparent`);
  
    // Clean up temporary file
    fs.removeSync(mmdPath);
  
    return `./${svgFilename}`;
  }
docs: Accepts the `source` of the graph as a string, and render an SVG using
  mermaid.cli. Returns the path to the rendered SVG.
  
  @param  {string} source
  @param  {string} destination
  @return {string}