[css-flexbox-1][editorial] Link to startmost/endmost

Author: tabatkins

css-flexbox-1/Overview.bs

@@ -2289,7 +2289,7 @@ Flex Container Baselines</h3>
 			2. Otherwise, if the flex container has at least one <a>flex item</a>,
 				the flex container's first/last <a>main-axis baseline set</a>
 				is <a lt="generate baselines">generated</a> from
-				the <a>alignment baseline</a> of the startmost/endmost <a>flex item</a>.
+				the <a>alignment baseline</a> of the [=startmost=]/[=endmost=] <a>flex item</a>.
 				(If that item has no <a>alignment baseline</a>
 				parallel to the flex container's <a>main axis</a>,
 				then one is first <a lt="synthesized baseline">synthesized</a>