DOC-3267: Deprecate content_css_cors option (#3835)

* DOC-3267: Deprecate content_css_cors option

* DOC-3209: Add missing release note mention.

---------

Co-authored-by: Karl Kemister-Sheppard <[email protected]>

Author: michalnieruchalski-tiugo

modules/ROOT/pages/8.1.0-release-notes.adoc

@@ -407,6 +407,10 @@ This caused issues when opening such links, as the URLs became invalid. In {rele
 
 // placeholder here.
 
+=== The `content_css_cors` configuration option has been deprecated
+// #TINY-12578
+
+As of {productname} {release-version}, the `content_css_cors` configuration option has been marked as *deprecated*. It will be completely removed in the upcoming {productname} 9.0 release. As an alternative, we recommend using xref:tinymce-and-cors.adoc#crossorigin[crossorigin] instead.
 
 [[known-issues]]
 == Known issues

modules/ROOT/partials/configuration/content_css_cors.adoc

@@ -1,6 +1,8 @@
 [[content_css_cors]]
 == `+content_css_cors+`
 
+IMPORTANT: This option has been marked as *deprecated*. It will be completely removed in the upcoming {productname} 9.0 release. As an alternative, we recommend using xref:tinymce-and-cors.adoc#crossorigin[`crossorigin`] instead.
+
 When `+content_css_cors+` is set to `+true+`, the editor will add a `+crossorigin="anonymous"+` attribute to the link tags that the StyleSheetLoader uses when loading the `+content_css+`. This allows you to host the `+content_css+` on a different server than the editor itself.
 
 *Type:* `+Boolean+`