Announcement for 9.0.0-M1

[Andrea Del Bene]

Hi,

I'm working on the announcement for 9.0.0-M1. I'd like to have your 
opinion about it and  I need your help to better elaborate the "New and 
noteworthy" section. You can find it on web site repository:

https://github.com/apache/wicket-site/blob/asf-site/2019/_posts/wicket-9.0.0-M1-released.md

Thank you!