async _resolveSourcesList(sources) {
    const result = [];

    for (const source of sources) {
      if (typeof source === 'string') {
        result.push(source);
      } else if (source.esbuild) {
        result.push(await this._esbuildSource(
          path.resolve(this.opts.appDir, source.path),
          source.esbuildPlugins)
        );
      } else {
        result.push(...loadFiles(path.resolve(this.opts.appDir, source.path)));
      }
    }

    return result;
  }
@param {Source[]} sources
@return {Promise<string[]>}