chore: add outline custom form-field control to mdc-form-field demo

In order to better test how custom form-field control's integrate with
the MDC-based form-field, the demo should render a custom form-field
control in all variants. Fill is already displayed.

Author: devversion

src/components-examples/material-experimental/mdc-form-field/index.ts

@@ -25,7 +25,7 @@ const EXAMPLES = [
     ReactiveFormsModule,
   ],
   declarations: [...EXAMPLES, MyTelInput],
-  exports: EXAMPLES,
+  exports: [...EXAMPLES, MyTelInput],
   entryComponents: EXAMPLES,
 })
 export class MdcFormFieldExamplesModule {

src/dev-app/mdc-input/mdc-input-demo.html

@@ -703,5 +703,13 @@ <h3>&lt;textarea&gt; with bindable autosize </h3>
   <mat-card-content>
     <h4>Custom control</h4>
     <form-field-custom-control-example></form-field-custom-control-example>
+    <p>
+      <mat-form-field appearance="outline">
+        <mat-label>Phone number</mat-label>
+        <example-tel-input required></example-tel-input>
+        <mat-icon matSuffix>phone</mat-icon>
+        <mat-hint>Include area code</mat-hint>
+      </mat-form-field>
+    </p>
   </mat-card-content>
 </mat-card>