feat: Add paired list element style

- .block for list elements
- Taken from demo_module

elements/_grouping.scss

@@ -141,6 +141,11 @@ dl,
 ul,
 ol {
 	margin: config.$space_double 0;
+
+	&.block {
+		padding: 1em 5em;
+		background-color: config.$color_darker;
+	}
 }
 
 ul,
@@ -299,6 +304,17 @@ div {
 	&.inline {
 		@extend %flex-inline;
 	}
+
+	&.stretch {
+		flex-flow: row wrap;
+		align-items: stretch;
+		justify-content: space-between;
+		gap: config.$space_half config.$space_basic;
+
+		& > * {
+			flex: auto;
+		}
+	}
 }
 
 // Grid