Replace Sass @import usage with @forward

[rmkane]

The use of @import is discouraged. Utilize the @use rule instead.

See: https://sass-lang.com/documentation/at-rules/import

"The Sass team discourages the continued use of the @import rule. Sass will gradually phase it out over the next few years, and eventually remove it from the language entirely. Prefer the @use rule instead."

I have addressed this in the following PR: https://github.com/oxalorg/sakura/pull/105