If the CSS for the admin theme is built well this will be really easy to implement. Since that's a goal I have anyway, this is a gimme.

This will be great for those of us that want to have smaller UI as well as a great feature for accessibility. Low vision people's gotsta edit websites too!

... mayhaps a high contrast setting too...

Just had a full day training on accessbility and that and this issue cemented my belief that we should (almost) never use PX in CSS for better flexibility and accessibility.

For a user that increases the default font-size: - If we use PX for our fonts, our text size will be uneffected. - If we use REM/EM for our fonts, but PX for our breakpoints we could be giving the user a broken experience, for example 3-word line lengths in a sidebar that would go away if the site was at a smaller breakpoint. - Using REM/EM for your font-sizes and breakpoints will give users that increase font size 125% an (almost) identical experience as a user that zoomed into the page 125%. (The EMs still have it.)

The issue that could come up unintended EM inheritance, but I think I have a strategy to prevent that from being a problem. Just need to iron some things out.

PR by @wesruv:

GitHub Issue #: