Add center and grid stack components.

assets/sass/components/center/_center.scss

@@ -0,0 +1,12 @@
+.grid-center {
+  display: grid;
+  place-items: center;
+}
+
+.text-center {
+  text-align: center;
+}
+
+.margin-center {
+  margin-inline: auto;
+}

assets/sass/components/grid-group/_grid-group.scss

@@ -5,10 +5,11 @@
 
   display: grid;
   gap: var(--gap);
-  grid-template-columns: repeat(auto-fit, minmax(var(--column-min), 1fr));
+  // Writing "Min" instead of "min" to force use of css "min()" instead of sass "min()".
+  grid-template-columns: repeat(auto-fit, minmax(Min(var(--column-min), 100%), 1fr));
 
   &--fill {
-    grid-template-columns: repeat(auto-fill, minmax(var(--column-min), 1fr));
+    grid-template-columns: repeat(auto-fill, minmax(Min(var(--column-min), 100%), 1fr));
   }
 
   &--100 {

assets/sass/components/grid-stack/_grid-stack.scss

@@ -0,0 +1,9 @@
+.grid-stack,
+%grid-stack {
+  display: grid;
+
+  & > * {
+    grid-column: 1 / 2;
+    grid-row: 1 / 2;
+  }
+}

assets/sass/styles.scss

@@ -30,6 +30,7 @@
 @import 'components/box/box';
 @import 'components/button/button';
 @import 'components/cards/cards';
+@import 'components/center/center';
 @import 'components/clearfix/clearfix';
 @import 'components/cookieconsent/cookieconsent';
 @import 'components/divider/divider';
@@ -37,6 +38,7 @@
 @import 'components/flex-group/flex-group';
 @import 'components/flex-inline/flex-inline';
 @import 'components/grid-group/grid-group';
+@import 'components/grid-stack/grid-stack';
 @import 'components/header/header';
 @import 'components/hidden/hidden';
 @import 'components/highlight-mark/highlight-mark';