Improve release post for mobile screens

Our release post looks great on big screens, but do demand some improvements for mobile.

Header

Until some time ago, we had as guideline that the title of the post should have only 2 feature names, the top features for CE and EE ("Feature A and Feature B"). Now, the marketing guideline says 2-3 features. The header container wasn't designed to have a huge headline, so, if we maintain 2-3 features, we need to adapt the layout. @williamchia do you confirm that we should maintain 2-3 features? Regardless, we need to set a max-char number for the headline and make it display entirely on any screen size.

Problem reported on twitter and on #3409 (closed)	How it displays on iPhone 7
Headline and author name cutted off, end of headline overlays the content container	Author name behind the nav bar

Alignment

h2 and h3 should be left-aligned to match the badges and the docs/issues buttons

Space between feature blocks

Secondary features and deprecations should include a separator (hr) as the primary features do. They should also have the same spacing between feature blocks:

Primary	Secondary	Deprecations

Anything else?

@jareko could you please take point and help us here?

@axil as you're the tech writing leading 11.6, can you please follow-up here?

@dimitrieh @luke any notes?