New rule idea: Forbid @import use

[Christian24]

Hello,

Given the sass team's discouragement to use @import: I think it would be helpful to have a rule ensuring that @import isn't used in a project.

This certainly wouldn't be part of the default rule set, but it would help folks who ran sass-migrator in their codebase to keep it consistent.

[stof]

Note that this rule should still allow @import when Sass emits it as a CSS import (the logic for that already exists in the implementation of the partial-no-import rule)