[css-color-6] Add note wrt multiple contrast algorithms

Co-Authored-By: fantasai <725717+fantasai@users.noreply.github.com>

css-color-6/Overview.bs

@@ -67,8 +67,11 @@ Computing a Contrasting Color: the ''contrast-color()'' function {#colorcontrast
 		  [ [ <<color>> && [ tbd-fg | tbd-bg ] && <<target-contrast>>? ] |
 		    [ <<color>> && [ tbd-fg | tbd-bg ] && <<target-contrast>>, <<color>># ] )
 		<<target-contrast>> = <<wcag2>>
+		<!-- Allow multiple algorithms in the future by using && operator instead of | for <<target-contrast>> additions.
+		See resolution in #7357 -->
 	</pre>
 
+
 	The only mandatory argument is the <dfn lt="contrast base color" local-lt="base color">base color</dfn>
 	against which the contrast is computed.
 	This is typically (but not necessarily) a background color.