Form: add 'Customize a Validation Icon' (DevExpress#6375) (DevExpress#6376)

Author: vladaskorohodova

concepts/05 UI Components/Form/40 Customize a Validation Icon.md

@@ -0,0 +1,14 @@
+To customize the validation icon, modify the `dx-texteditor-input-container` class. To shift the icon's position to the left, apply these CSS rules:
+
+    <!--CSS-->
+    .dx-texteditor.dx-invalid .dx-texteditor-input-container::after {
+        left: 4px;
+        right: 0;
+    }
+
+    .dx-texteditor.dx-invalid .dx-texteditor-input {
+        padding-right: 0;
+        padding-left: 34px;
+    } 
+
+[Examine CSS](/Documentation/Guide/Troubleshooting/Basics/#Examine_CSS) if further customization is required.