fix(scss): Dart Sass 3.0.0 compatibility

fixes #7772
fixes #7771

Author: nolimits4web

src/core/core.scss

@@ -1,6 +1,6 @@
 @at-root {
   :root {
-    --swiper-theme-color: #{$themeColor};
+    --swiper-theme-color: #{vars.$themeColor};
     /*
     --swiper-preloader-color: var(--swiper-theme-color);
     --swiper-wrapper-transition-timing-function: initial;

src/modules/navigation/navigation.scss

@@ -1,4 +1,4 @@
-@import '../../swiper-vars.scss';
+@use '../../swiper-vars.scss' as vars;
 @at-root {
   :root {
     --swiper-navigation-size: 44px;

src/modules/pagination/pagination.scss

@@ -1,4 +1,4 @@
-@import '../../swiper-vars.scss';
+@use '../../swiper-vars.scss' as vars;
 @at-root {
   :root {
     /*

src/swiper.scss

@@ -1,4 +1,4 @@
-@import 'swiper-vars.scss';
+@use 'swiper-vars.scss' as vars;
 @at-root {
   @font-face {
     font-family: 'swiper-icons';