WIP:feat: implement comment notifications for link page

[LIlGG]

What type of PR is this?

/kind feature

What this PR does / why we need it:

为 link 页面新增评论通知。

How to test it?

测试在 link 页面进行评论后是否会发送邮件通知。

Which issue(s) this PR fixes:

Fixes #82 Fixes #89

Does this PR introduce a user-facing change?

为 Link 页面新增评论通知