old_contents: const config = {
    dir: 'dist',
    sanitizeFileName: (f) => f.includes('tXml') ? f.toLowerCase() : f,
  };
  
  export default {
    input: ['index.js', 'tXml.js', 'transformStream.js'],
    output: [
      {
        ...config,
        format: 'cjs',
        entryFileNames: '[name].js',
      },
      {
        ...config,
        format: 'esm',
        entryFileNames: '[name].mjs',
      },
    ],
    external: [
      'through2'
    ]
  };
  
new_contents: const config = {
    dir: 'dist',
    // Small hack to lowercase tXml in bundle
    sanitizeFileName: (f) => f.includes('tXml') ? f.toLowerCase() : f,
  };
  
  export default {
    input: ['index.js', 'tXml.js', 'transformStream.js'],
    output: [
      {
        ...config,
        format: 'cjs',
        entryFileNames: '[name].js',
      },
      {
        ...config,
        format: 'esm',
        entryFileNames: '[name].mjs',
      },
    ],
    external: [
      'through2'
    ]
  };
  
subject: Add comment on sanitizeFileName option