function createProcessor(pluginsListOrMap, options)
{
    if (!postcss) {
        return null;
    }

    const plugins = parsePlugins(pluginsListOrMap, options);

    return postcss(plugins);
}
Attempts to create a PostCSS Processor with the given plugins and options.

@param {PluginCollection} pluginsListOrMap - A list or map of plugins.
    If a map of plugins, the plugin name looks up `options`.
@param {PostCSSOptions}   options - The PostCSS wrapper options.

@returns {Processor|null}