[css-highlights-api] Fix markup

Author: frivoal

css-highlight-api-1/Overview.bs

@@ -266,15 +266,15 @@ Registering Custom Highlights</h3>
 		</xmp>
 
 		In the example above,
-		the same [=custom highlight=] object is [=registered=] under the names 'foo' and 'bar'.
+		the same [=custom highlight=] object is [=registered=] under the names <code>foo</code> and <code>bar</code>.
 		Since each of the [=style rules=] target the same highlight and have the same [=specificity=],
 		authors might expect the last rule to win in cascading order
 		and the highlighted content to be green.
 		However, each highlight name gets an independent set of highlight styles,
 		and the highlight will be painted once per name.
-		In this case, because 'foo' was registered before 'bar',
-		the highlight will be first painted with 'foo''s color (green)
-		and then with 'bar''s color (red).
+		In this case, because <code>foo</code> was registered before <code>bar</code>,
+		the highlight will be first painted with <code>foo</code>'s color (green)
+		and then with <code>bar</code>'s color (red).
 		As a result, the highlighted content will appear red.
 	</div>