About section: improve formatting on Features page

[tellyworth]

​https://wordpress.org/about/features/ has some quirky formatting of its dot-point headings.

Quoting @mapk from https://meta.trac.wordpress.org/ticket/3046#comment:136:

But yes, I think there should be a line break after each one since the words in bold aren't part of the sentence. Something like:

Simplicity
Simplicity makes it possible for you to get online and...

[dd32]

Adding the following makes the page feel a little nicer:

• A line break after </strong>
• A line break after the </li>

Simply adding a line break after </strong> doesn't work too well which is why i didn't change it at the time.

[dd32]

In 7073:

Main: Features: Add a line break after the section title and after each dotpoint.

Fixes #3558.

[dd32]

In 7074:

Main: Features: Add missing sass component from r7073

See #3558.