fix-next(css): className to preserve root views classes (#7725)

tns-core-modules/css/system-classes.d.ts

@@ -0,0 +1,30 @@
+/**
+ * @module "system-classes"
+ */ /** */
+
+/**
+ * String value "ns-" used for CSS system class prefix.
+ */
+export const CLASS_PREFIX: string;
+
+/**
+ * Gets CSS system class for modal root view.
+ */
+export function getModalRootViewCssClass(): string;
+
+/**
+ * Gets CSS system classes for root view.
+ */
+export function getRootViewCssClasses(): string[];
+
+/**
+ * * Appends new CSS class to the system classes and returns the new length of the array.
+ * @param value New CSS system class.
+ */
+export function pushToRootViewCssClasses(value: string): number;
+
+/**
+ * Removes CSS class from the system classes and returns it.
+ * @param value
+ */
+export function removeFromRootViewCssClasses(value: string): string;