Added container mixin with responsive sizes

Implemented a new SCSS mixin named 'container' to handle different container sizes: small, medium, and large. This mixin allows for dynamic styling based on the specified size parameter. Styles for 'small' and 'large' sizes are structured for future customization, while the 'medium' size is currently set with a max-width of 1440px and centered margin.

base.scss

@@ -1,6 +1,7 @@
 @import "./src/styles/scss/reset";
 @import "./src/stories/Library/colors/color-variables";
 @import "./src/styles/scss/skeleton";
+@import "./src/styles/scss/container";
 
 // The imports below are not advised to be moved around, because
 // they cross-reference various defined variables between each other.

src/styles/scss/container.scss

@@ -0,0 +1,10 @@
+@mixin container($size) {
+  @if $size == small {
+    // Styles for small size
+  } @else if $size == medium {
+    max-width: 1440px;
+    margin: 0 auto;
+  } @else if $size == large {
+    // Styles for large size
+  }
+}