Update README.md

[MickL]

In Tailwind 3 and 4 there is no xs breakpoint with 320px width, rather everything below 640 is the considered to be the default. I therefor lowered xs width to 0. I was also considering to rename xs to default, what do you think?

I also updated xs to be the fallback as Tailwind is mobile first this should be the default/fallback.

[mvrlin]

Hey! Sorry for the late response 😅
Yes, you're right. I made xs to be the same as the default mobile. We can use 0, sure.
About the fallback, it all depends on your needs. It makes sense if you have more mobile devices than desktop devices to use xs.