chore(css): Add grunttask to fix content-server Tailwind selectors

[LZoog]

Because:

• Our content-server CSS minification build task is stripping a space between brackets and asterisks, invalidating the selector and causing some styles to not apply. See comment included in commit for more details

This commit:

• Adds a grunttask to add the whitespace back

fixes FXA-9167, fixes FXA-9170

---

In #16445, I wondered if removing --minify would not fix the problem (see the "EDIT" and comments). We included the fix in a dot release and I've since confirmed a few things:

• Stage is still having the problems described in the linked tickets
• --minify does not do anything for us for content-server at least, I compared what was uploaded to stage before and after this option and there is no diff because...
• We're using a grunt task to minify our content-server CSS not handled by webpack
• This bug was introduced because of the recent Tailwind upgrade, see this. Before this upgrade, our ltr and rtl classes did not produce :where([dir="ltr"], [dir="ltr"] *) selectors. It's possible this selector output (specifically the asterisk) is a bug in Tailwind but I'd need to do more investigating.

I tried every available formatting option for the cssmin task and also tried tweaking the level to prevent needing a new task, and nothing addressed this problem. I also tried excluding the Tailwind file from the cssmin task but couldn't get this to work.

I started adjusting the classes themselves to not use these selectors, but we've got a few that we'd have to change to something like [dir='rtl'] & {, and then we'd have to know and abide by not use these Tailwind classes in content-server due to the minify problem.

This seemed like a reasonable solution for now since we hope to sunset content-server soon anyway. Other options were described above, or downgrading Tailwind and pinning us to a version until we've sunsetted content-server or until/unless they tweak the selector.

This fix can be verified by running yarn build before and after this change in content-server and checking the dist/styles/[hash].tailwind.out.css file. See that before, there are several ]* references and after, they've become ] *.

[vpomerleau]

LGTM! Thanks for all your investigation on this, was not as straightforward as it first appeared.

I've compared the before/after files with diff checker (only difference is ]* --> ] * as expected).