[selectors-4] Add more issue links.

Author: fantasai

selectors-4/Overview.bs

@@ -1085,6 +1085,7 @@ The Matches-any Pseudo-class: '':matches()''</h3>
 	'':matches(ul, ol, .list) > [hidden]'' and ''ul > [hidden], ol > [hidden], .list > [hidden]''
 	are equivalent in both their matching behavior and specificity.
 	See [[#specificity-rules]].
+	ISSUE: See also <a href="https://github.com/w3c/csswg-drafts/issues/1027">issue 1027</a>.
 
 	Pseudo-elements cannot be represented by the matches-any pseudo-class;
 	they are not valid within '':matches()''.
@@ -2150,6 +2151,12 @@ The Input Focus Pseudo-class: '':focus''</h3>
 	if made to propagate due to other mechanisms,
 	but not merely due to being the parent.)
 
+	ISSUE: There's a desire from authors to propagate '':focus''
+	from a form control to its associated <{label}> element;
+	the main objection seems to be implementation difficulty.
+	See <a href="https://github.com/w3c/csswg-drafts/issues/397">CSSWG issue (CSS)</a>
+	and <a href="https://github.com/whatwg/html/issues/1632">WHATWG issue (HTML)</a>.
+
 <h3 id="the-focus-visible-pseudo" oldids="the-focusring-pseudo,focus-ring-pseudo">
 The Focus-Indicated Pseudo-class: '':focus-visible''</h3>
 
@@ -3196,6 +3203,8 @@ Calculating a selector's specificity</h2>
 	A few pseudo-classes provide “evaluation contexts” for other selectors,
 	and so have their specificity defined by their contents and how they match:
 
+	ISSUE: See also <a href="https://github.com/w3c/csswg-drafts/issues/1027">issue 1027</a>.
+
 	<ul>
 		<li>
 			The specificity of a '':matches()'' pseudo-class is replaced by