style editor overlay label

src/Umbraco.Web.UI.Client/src/less/components/umb-property-editor.less

@@ -7,7 +7,6 @@
 }
 
 .umb-property-editor__overlay {
-    content: "";
     background-color: rgba(255,255,255, .65);
     display: block;
     position: absolute;
@@ -16,6 +15,18 @@
     width: 100%;
     height: 100%;
     z-index: 1;
+    display: flex;
+    justify-content: center;
+    align-items: center;
+}
+
+.umb-property-editor__overlay-label {
+    font-size: 16px;
+    font-weight: bold;
+    color: #;
+    background: #ffffff;
+    padding: 10px 20px;
+    color: @grayLight;
 }