[css-fonts-5][editorial] Add some useful issue links

Author: svgeesus

css-fonts-5/Overview.bs

@@ -126,6 +126,8 @@ Relative sizing: the 'font-size-adjust' property</h3>
 	and will thus appear to be a different size
 	and possibly be less readable.
 
+Issue(8792):
+
 	The 'font-size-adjust' property provides a way
 	to preserve the readability and apparent size of text
 	when font fallback occurs.
@@ -485,6 +487,8 @@ the 'size-adjust' descriptor</h3>
 	such as ''em'' units, percentages in 'text-underline-offset', etc.)
 	remains unaffected.
 
+Issue(8967):
+
 	Note: The 'size-adjust' descriptor functions similarly to
 	the 'font-size-adjust' property,
 	which essentially calculates an adjustment per font by matching ex heights,