[css-align-3][editorial] Fix indentation, add emphasis.

Author: fantasai

css-align-3/Overview.bs

@@ -2010,18 +2010,18 @@ Default Alignment Shorthand: the 'place-items' property</h3>
 <h2 id='gaps'>
 Gaps Between Boxes</h2>
 
-While 'margin' and 'padding' can be used to specify visual spacing around individual boxes,
-it's sometimes more convenient to globally specify spacing between adjacent boxes
-within a given layout context,
-particularly when the spacing is different between boxes
-as opposed to between the first/last box and the container's edge.
-
-The 'gap' property,
-and its 'row-gap' and 'column-gap' sub-properties,
-provide this functionality for
-<a href="http://www.w3.org/TR/css3-multicol/">multi-column</a>,
-<a href="http://www.w3.org/TR/css-flexbox/">flex</a>,
-and <a href="http://www.w3.org/TR/css-grid/">grid layout</a>.
+	While 'margin' and 'padding' can be used to specify visual spacing around individual boxes,
+	it's sometimes more convenient to globally specify spacing
+	<em>between</em> adjacent boxes within a given layout context,
+	particularly when the spacing is different between sibling boxes
+	as opposed to between the first/last box and the container's edge.
+
+	The 'gap' property,
+	and its 'row-gap' and 'column-gap' sub-properties,
+	provide this functionality for
+	<a href="http://www.w3.org/TR/css3-multicol/">multi-column</a>,
+	<a href="http://www.w3.org/TR/css-flexbox/">flex</a>,
+	and <a href="http://www.w3.org/TR/css-grid/">grid layout</a>.
 
 <h3 id='column-row-gap'>
 Row and Column Gutters: the 'row-gap' and 'column-gap' properties</h3>