docs: BottomNavigation example

Author: NickIliev

…-navigation/button-examples.component.ts …/bottom-navigation-examples.component.tsapp/ng-ui-widgets-category/bottom-navigation/button-examples.component.ts renamed to app/ng-ui-widgets-category/bottom-navigation/bottom-navigation-examples.component.ts app/ng-ui-widgets-category/bottom-navigation/button-examples.component.ts renamed to app/ng-ui-widgets-category/bottom-navigation/bottom-navigation-examples.component.ts

@@ -1,7 +1,7 @@
 import { NgModule, NO_ERRORS_SCHEMA } from "@angular/core";
 import { NativeScriptRouterModule } from "nativescript-angular/router";
 import { NativeScriptCommonModule } from "nativescript-angular/common";
-import { BottomNavigationExamplesComponent } from "./button-examples.component";
+import { BottomNavigationExamplesComponent } from "./bottom-navigation-examples.component";
 import { UsageComponent } from "./usage/usage.component";
 import { NativeScriptFormsModule } from "nativescript-angular/forms";
 import { TitleAndNavButtonModule } from "../../directives/title-and-nav-button.module";

app/ng-ui-widgets-category/bottom-navigation/bottom-navigation-examples.module.ts

@@ -1,2 +1,8 @@
+The `BottomNavigation` component contains two sub-components:
+- The `TabStrip` which defines and rendres the bottom bar and its `TabStripItem` components.
+- Multiple `TabContentItem` components which total number should be equal to the number of the tabs (`TabStripItem` components). Each `TabContentItem` acts as a container for your tab content.
 
 <snippet id='bottom-navigation-usage-html'/>
+
+> **Note:** The number of `TabStripItem` components must be equal to the number of `tabContentItem` components.
+