Fix: Block movers don't appear on the playground and on the widgets p…

…age. (#15076)

The keyframe animations contained a comment saying they need to be duplicated, but they were not being duplicated in widgets and playground styles this made the block movers invisible.

packages/edit-widgets/src/style.scss

@@ -40,3 +40,31 @@ body.gutenberg_page_gutenberg-widgets {
 		height: 100%;
 	}
 }
+
+/**
+ * Animations
+ */
+
+// These keyframes should not be part of the _animations.scss mixins file.
+// Because keyframe animations can't be defined as mixins properly, they are duplicated.
+// Since hey are intended only for the editor, we add them here instead.
+@keyframes edit-post__loading-fade-animation {
+	0% {
+		opacity: 0.5;
+	}
+	50% {
+		opacity: 1;
+	}
+	100% {
+		opacity: 0.5;
+	}
+}
+
+@keyframes edit-post__fade-in-animation {
+	from {
+		opacity: 0;
+	}
+	to {
+		opacity: 1;
+	}
+}

playground/src/style.scss

@@ -35,3 +35,31 @@
 		height: 100%;
 	}
 }
+
+/**
+ * Animations
+ */
+
+// These keyframes should not be part of the _animations.scss mixins file.
+// Because keyframe animations can't be defined as mixins properly, they are duplicated.
+// Since hey are intended only for the editor, we add them here instead.
+@keyframes edit-post__loading-fade-animation {
+	0% {
+		opacity: 0.5;
+	}
+	50% {
+		opacity: 1;
+	}
+	100% {
+		opacity: 0.5;
+	}
+}
+
+@keyframes edit-post__fade-in-animation {
+	from {
+		opacity: 0;
+	}
+	to {
+		opacity: 1;
+	}
+}