NEWS: add old entry about Type=ether

Apparently it's an important feature for some folks:
https://utcc.utoronto.ca/\~cks/space/blog/linux/NetworkdMACMatchesWidely.
I think we considered this more of a bugfix, but it's somewhere on the border.
Let's add this it's easier to discover.

(cherry picked from commit 88b2a950)
(cherry picked from commit 3cb75aec)
(cherry picked from commit 3f96f2a7)