Add an integration hub page to replace the https://www.pingcap.com/integrations/

[likidu]

Proposed by Marketing team to redesign the integration hub page in docs to replace the current https://www.pingcap.com/integrations/

https://pingcap-cn.feishu.cn/wiki/NzLZwDWBlir859kPzZkcmAQynSb?comment_id=7410875800481693699&comment_type=0&comment_anchor=true