Bootswatch wrong order in subtheme.style.scss

Hi!

In the subtheme's [subtheme].style.scss, I think the line @import "bootswatch/variables"; should be placed before @import "bootstrap/variables".

Because all variables has a "!default" suffix. That means if the current variable wasn't set before, take the new value. But in this order, every variables are already set. So bootswatch variables will never be considered.

If you go to https://bootswatch.com/, the .sass variables file has !default everywhere. So I guess that means we should use it this way ... Anyhow, I would still be nice to have a "custom_variables.scss" to overwrite (without any use of "!default") any variables without touching the bootswatch files. That's my suggestion :)

Thanks!