【Requirements for new features】Support email subscription

[jianshuod]

Easy to understand.
Send emails concerning what they like to the subscribers.

[jacklightChen]

The website currently supports Google/iCloud Calendar subscription. However, adding the email subscription feature to the static website appears to be burdensome. We may consider adding the feature to the WeChat applet if possible.

[jacklightChen]

There used to be a third-party email subscription service for ccfddl, but now it is no longer maintained. We attempt to contact the author to find if we could continue the service.

https://ccf.hustpdsl.cn/

[jacklightChen]

The third-party email subscription have continued at https://ccf.jianyue.tech/, and we also plan to host the service.