crawler

A minor cleanup for the future.

At the moment we use this in http11.py:

with suppress(AttributeError):
    txresponse._transport._producer.loseConnection()

[Once we drop support for Twisted < 18.4.0](twisted/twisted@3855923

Bug 描述
访问前端页面时，会有两个请求404

复现步骤
该 Bug 复现步骤如下

1. 使用官方文档中的ym启动docker-compose
2. 访问前端页面
3. 弹出请求失败404

期望结果
xxx 能工作。

截屏

In the quick start section, it seems forgot to mention the pipeline setting, and without the setting seems will cause yield item appear wrong result. Just like #137, please update the document, if need help, I can do the contribution as well.

Unless I missed something, the documentation doesn't explain how to query document metadata (searching "site:montferret.dev metadata" through Google returned nothing, neither did grepping the source code).

As an example, I tried to query the og:url metadata.
I tried variations of //meta[property='og:url']::attr(content), with or without the leading //, and with or without the `attr(conte