[css-box-3][css-break-4] Cross-reference margin-trim & margin-break.

Author: fantasai

css-box-3/Overview.bs

@@ -362,6 +362,11 @@ Margins at Container Edges: the 'margin-trim' property {#margin-trim}
 
 	ISSUE: Should floats have a <css>floats</css> value that only affects floats?
 
+	Note: See also the 'margin-break' property,
+	which applies to the box’s own margins
+	when they adjoin a <a>fragmentation break</a>
+	(page break / column break / etc.).
+
 Padding {#paddings}
 =======
 

css-break-4/Overview.bs

@@ -97,6 +97,9 @@ Adjoining Margins at Breaks: the 'margin-break' property</h3>
 			including at the start and end of a <a>fragmentation context</a>.
 	</dl>
 
+	Note: See also the 'margin-trim' property,
+	which applies to the <a>fragmentation container</a> (page/column/etc.)
+
 	ISSUE: <a href="https://www.antennahouse.com/product/ahf66/ahf-focss6.html">Antenna House also allows a second <css>keep</css> keyword</a>,
 	which preserves the margin after the break;
 	it is otherwise discarded.