Split grid & containers (#29146)

scss/mixins/_container.scss

@@ -0,0 +1,19 @@
+// Container mixins
+
+@mixin make-container($padding-x: $container-padding-x) {
+  width: 100%;
+  padding-right: $padding-x;
+  padding-left: $padding-x;
+  margin-right: auto;
+  margin-left: auto;
+}
+
+
+// For each breakpoint, define the maximum width of the container in a media query
+@mixin make-container-max-widths($max-widths: $container-max-widths, $breakpoints: $grid-breakpoints) {
+  @each $breakpoint, $container-max-width in $max-widths {
+    @include media-breakpoint-up($breakpoint, $breakpoints) {
+      max-width: $container-max-width;
+    }
+  }
+}