LibWeb/CSS: Implement the color-scheme CSS property

Author: https://github.com/Gingeh
Commit: ce5cd012b9
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/3146
Reviewed-by: https://github.com/AtkinsSJ ✅

Libraries/LibWebView/ProcessManager.cpp

@@ -130,12 +130,6 @@ String ProcessManager::generate_html()
         <title>Task Manager</title>
         <style>
                 @media (prefers-color-scheme: dark) {
-                    /* FIXME: We should be able to remove the HTML style when "color-scheme" is supported */
-                    html {
-                        background-color: rgb(30, 30, 30);
-                        color: white;
-                    }
-
                     tr:nth-child(even) {
                         background: rgb(57, 57, 57);
                     }
@@ -147,6 +141,10 @@ String ProcessManager::generate_html()
                     }
                 }
 
+                html {
+                    color-scheme: light dark;
+                }
+
                 table {
                     width: 100%;
                     border-collapse: collapse;

Libraries/LibWebView/SourceHighlighter.h

@@ -79,13 +79,6 @@ String highlight_source(URL::URL const& url, URL::URL const& base_url, StringVie
 
 constexpr inline StringView HTML_HIGHLIGHTER_STYLE = R"~~~(
     @media (prefers-color-scheme: dark) {
-        /* FIXME: We should be able to remove the HTML style when "color-scheme" is supported */
-        html {
-            background-color: rgb(30, 30, 30);
-            color: white;
-            counter-reset: line;
-        }
-
         :root {
             --comment-color: lightgreen;
             --keyword-color: orangered;
@@ -111,6 +104,10 @@ constexpr inline StringView HTML_HIGHLIGHTER_STYLE = R"~~~(
         }
     }
 
+    html {
+        color-scheme: light dark;
+    }
+
     .html {
         font-size: 10pt;
         font-family: Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;