LibWeb: Improve user-select support

Author: https://github.com/Psychpsyo
Commit: eb7824339b
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/3139
Reviewed-by: https://github.com/AtkinsSJ ✅

Libraries/LibWeb/CSS/Default.css

@@ -893,3 +893,8 @@ input[type=checkbox][switch]:checked::before {
 input[type=checkbox][switch]:checked {
 	background-color: AccentColor;
 }
+
+/* https://drafts.csswg.org/css-ui/#propdef-user-select */
+button, meter, progress, select {
+    user-select: none;
+}

Libraries/LibWeb/CSS/Properties.json

@@ -130,6 +130,9 @@
   "-webkit-transition-timing-function": {
     "legacy-alias-for": "transition-timing-function"
   },
+  "-webkit-user-select": {
+    "legacy-alias-for": "user-select"
+  },
   "accent-color": {
     "animation-type": "by-computed-value",
     "inherited": true,