Merge pull request scrapy#1643 from orangain/doc-downloader-middleware-base-1.0

DOC: Add AjaxCrawlMiddleware to DOWNLOADER_MIDDLEWARES_BASE

Author: kmike

docs/topics/settings.rst

@@ -341,6 +341,7 @@ Default::
         'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware': 400,
         'scrapy.downloadermiddlewares.retry.RetryMiddleware': 500,
         'scrapy.downloadermiddlewares.defaultheaders.DefaultHeadersMiddleware': 550,
+        'scrapy.downloadermiddlewares.ajaxcrawl.AjaxCrawlMiddleware': 560,
         'scrapy.downloadermiddlewares.redirect.MetaRefreshMiddleware': 580,
         'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware': 590,
         'scrapy.downloadermiddlewares.redirect.RedirectMiddleware': 600,