[css-inline-3] Improve selectors in UA default styles for initial-letter-align, add some script subtag rules.

Author: fantasai

css-inline-3/Overview.bs

@@ -805,22 +805,26 @@ UA Default Stylesheet for 'initial-letter-align'</h4>
 	UAs must include in their default UA style sheet the following rules:
 
 	<pre>
-		[lang=zh], [lang=ja], [lang=ko], [lang=ii] {
+		[lang]:lang(zh, ja, ko, ii) {
 		  initial-letter-align: ideographic;
 		}
-		[lang|=iw], [lang|=yi], [lang|=lad], [lang|=jrb] {
+		[lang]:lang(iw, yi, lad, jrb) {
 		  initial-letter-align: hebrew;
 		}
-		[lang|=hi], [lang|=mr], [lang|=ne], , [lang|=pi], [lang|=kok], [lang|=brx], [lang|=mai], [lang|=sd], [lang|=sa] {
+		[lang]:lang(hi, mr, ne, pi, kok, brx, mai, sd, sa) {
 		  initial-letter-align: hanging;
 		}
+		/* Script tags override language tags */
+		[lang]:lang('*-Latn', '*-Cyrl') {
+		  initial-letter-align: alphabetic;
+		}
+		[lang]:lang('*-Hani', '*-Hant', '*-Hans') {
+		  initial-letter-align: ideographic;
+		}
 	</pre>
 
-	Issue: We don't have a way to do subtag selection with attr selectors.
-	(It's a feature of '':lang()'' in Selectors 4,
-	but we don't want to use that because we want to hit the language root,
-	not all of the descendant elements.)
-	These selectors should also include the relevant script subtags.
+	Issue: This only covers the most common cross-linguistic transcription systems.
+	Should we include any other / all script tags in the UA style sheet?
 
 <h3 id="sizing-initial-letters">
 Sizing Initial Letters</h3>