Fix styles for Windows high contrast mode

packages/edit-post/src/components/layout/style.scss

@@ -1,5 +1,7 @@
 .edit-post-meta-boxes-main {
 	filter: drop-shadow(0 -1px rgba($color: #000, $alpha: 0.133)); // 0.133 = $gray-200 but with alpha.
+	// Windows High Contrast mode will show this outline, but not the shadow.
+	outline: 1px solid transparent;
 	background-color: $white;
 	clear: both; // This is seemingly only needed in case the canvas is not iframe’d.
 	display: flex;
@@ -44,6 +46,9 @@
 			inset: var(--wp-admin-border-width-focus);
 			@include button-style__focus();
 		}
+		> svg {
+			fill: currentColor;
+		}
 	}
 
 	.is-resizable.edit-post-meta-boxes-main & {
@@ -58,6 +63,9 @@
 			&::before {
 				content: "";
 				background-color: $gray-300;
+				// Windows High Contrast mode will show this outline, but not the background-color.
+				outline: 2px solid transparent;
+				outline-offset: -2px;
 				position: absolute;
 				inset-block: calc(50% - #{$grid-unit-05} / 2) auto;
 				transform: translateX(-50%);