[ADD] web: bs5 utility-classes, add gaps

Define "Bootstrap v5 ready" utility-class to handle gaps.
This class definition can be safely removed after migrating to v5.

task-2733437

Part-of: odoo/odoo#82866

addons/web/static/src/libs/bs5_utility_classes.scss

@@ -32,3 +32,20 @@ $o-inline-spacers: map-merge($spacers, ('auto': auto));
 .float-end {
   float: right !important;
 }
+
+// == Gaps
+//------------------------------------------------------------------------------
+// "Bootstrap v5 ready" utility-classes to handle gaps.
+// These classes definitions can be safely removed after migrating to BTS v5.
+
+@each $breakpoint in map-keys($grid-breakpoints) {
+  @include media-breakpoint-up($breakpoint) {
+    $infix: breakpoint-infix($breakpoint, $grid-breakpoints);
+
+    @each $size, $length in $spacers {
+      .gap#{$infix}-#{$size} {
+        gap: $length !important;
+      }
+    }
+  }
+}