bug#51821: 29.0.50; Suggest add variable or frame parameter: line-height

[Eli Zaretskii]

> From: "Feng Shu" <tumashu@163.com>
> Cc: Lars Ingebrigtsen <larsi@gnus.org>,  51821@debbugs.gnu.org
> Date: Mon, 15 Nov 2021 06:42:39 +0800
> 
> What about support it as a face attr instead of variable?

I explained in a previous message why this cannot work at the face
level.

Anyway, we should first think about what the feature will do, not how
to specify it.  How to specify it will come next.