[css-align-3] capitalization

Author: tabatkins

css-align-3/Overview.bs

@@ -1679,7 +1679,7 @@ Baseline Self-Alignment</h3>
 
 	Boxes participating in row-like layout contexts (<a>shared alignment contexts</a>)
 	can be baseline-aligned to each other.
-	<dfn export lt="baseline self-alignment|first-baseline self-alignment|last-baseline self-alignment">baseline self-alignment</dfn> effectively increases the <strong>margins</strong> on the box
+	<dfn export lt="baseline self-alignment|first-baseline self-alignment|last-baseline self-alignment">Baseline self-alignment</dfn> effectively increases the <strong>margins</strong> on the box
 	to align its <a>alignment baseline</a>
 	with that of other baseline-aligned boxes in its <a>baseline-sharing group</a>.