add custom stepper guide to the guide list (#575)

Author: mmalerba

src/app/shared/guide-items/guide-items.ts

@@ -47,6 +47,11 @@ const GUIDES = [
     name: 'Using elevation helpers',
     document: '/docs-content/guides/elevation.html'
   },
+  {
+    id: 'creating-a-custom-stepper-using-the-cdk-stepper',
+    name: 'Creating a custom stepper using the CdkStepper',
+    document: '/docs-content/guides/creating-a-custom-stepper-using-the-cdk-stepper.html'
+  }
 ];
 
 @Injectable()

src/assets/stackblitz/material-module.ts

@@ -1,8 +1,9 @@
+import {A11yModule} from '@angular/cdk/a11y';
 import {DragDropModule} from '@angular/cdk/drag-drop';
 import {ScrollingModule} from '@angular/cdk/scrolling';
+import {CdkStepperModule} from '@angular/cdk/stepper';
 import {CdkTableModule} from '@angular/cdk/table';
 import {CdkTreeModule} from '@angular/cdk/tree';
-import {A11yModule} from '@angular/cdk/a11y';
 import {NgModule} from '@angular/core';
 import {
   MatAutocompleteModule,
@@ -45,6 +46,7 @@ import {
 @NgModule({
   exports: [
     A11yModule,
+    CdkStepperModule,
     CdkTableModule,
     CdkTreeModule,
     DragDropModule,