[Feature] Implement What's New Section

[asr2003]

Something from the user perspective, a user(this can be me) can be curious to see what's newly added to the Knative. For an instance, we have introduced this Bookstore tutorial or new releases or new events etc.. It can make a quick access and overview of the what's the latest news of Knative. Can we add any section of What's new?

If yes, we can add this beside Needs to Know more section, something it seems like we are using more space for it here:

Ref: knative/docs#6007 (comment)

[Cali0707]

Recommendation: add section recommending following social media for "what's new" announcements