fixup! chore(mixins): add a cross-browser reliable chessboard background mixin

Author: Kiarokh

src/style/mixins.scss

@@ -456,7 +456,7 @@ $clickable-normal-state-transitions: (
 * typically used to visualize transparency.
 */
 @mixin add-chessboard-background {
-    background-image: url('data:image/svg+xml;utf8,%3Csvg%20xmlns%3D%27http://www.w3.org/2000/svg%27%20viewBox%3D%270%200%208%208%27%20style%3D%27fill-rule:evenodd;%27%3E%3Cpath%20fill%3D%27rgba(186,186,192,0.16)%27%20d%3D%27M0%200h4v4H0zM4%204h4v4H4z%27/%3E%3C/svg%3E');
+    background-image: url('data:image/svg+xml;charset=UTF-8,%3Csvg%20xmlns%3D%27http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%27%20viewBox%3D%270%200%208%208%27%20style%3D%27fill-rule%3Aevenodd%3B%27%3E%3Cpath%20fill%3D%27rgba(186%2C186%2C192%2C0.16)%27%20d%3D%27M0%200h4v4H0zM4%204h4v4H4z%27%2F%3E%3C%2Fsvg%3E');
     background-size: 0.5rem;
 }