Fix w3c#2205 by referencing RFC8081 for collection fragment syntax

Author: svgeesus

css-fonts-4/Overview.bs

@@ -1376,15 +1376,15 @@ images/containing SVG font definitions.  If the element reference is omitted,
 a reference to the first defined font is implied.  Similarly, font
 container formats that can contain more than one font must load one
 and only one of the fonts for a given ''@font-face'' rule. Fragment
-identifiers are used to indicate which font to load.  If a container
-format lacks a defined fragment identifier scheme, implementations
-should use a simple 1-based indexing scheme (e.g. "font-collection#1"
-for the first font, "font-collection#2" for the second font).
+identifiers are used to indicate which font to load; these use the PostScript
+name of the font as defined in [[!RFC8081]].  </p>
 
 <pre>
-src: url(fonts/simple.woff);   /* load simple.woff relative to stylesheet location */
-src: url(/fonts/simple.woff);  /* load simple.woff from absolute location */
-src: url(images/fonts.svg#simple);    /* images/load SVG font with id 'simple' */
+src: url(fonts/simple.woff);       /* load simple.woff relative to stylesheet location */
+src: url(/fonts/simple.woff);      /* load simple.woff from absolute location */
+src: url(fonts/coll.otc#foo);      /* load font foo from collection coll.otc
+src: url(fonts/coll.woff2#foo);    /* load font foo from woff2 collection coll.woff2
+src: url(fonts.svg#simple);        /* load SVG font with id 'simple' */
 </pre>
 
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