docs(datepicker): improve and fix month picker example (#10008)

src/lib/chips/chip-list.ts

@@ -747,4 +747,3 @@ export class MatChipList extends _MatChipListMixinBase implements MatFormFieldCo
     });
   }
 }
-

src/material-examples/datepicker-views-selection/datepicker-views-selection-example.css

@@ -1 +1,7 @@
-/** No CSS for this example */
+.example-month-picker .mat-calendar-period-button {
+  pointer-events: none;
+}
+
+.example-month-picker .mat-calendar-arrow {
+  display: none;
+}

src/material-examples/datepicker-views-selection/datepicker-views-selection-example.html

@@ -1,6 +1,10 @@
 <mat-form-field>
   <input matInput [matDatepicker]="dp" placeholder="Month and Year" [formControl]="date">
   <mat-datepicker-toggle matSuffix [for]="dp"></mat-datepicker-toggle>
-  <mat-datepicker #dp (yearSelected)="chosenYearHandler($event)"
-                  (monthSelected)="chosenMonthHandler($event, dp)"></mat-datepicker>
+  <mat-datepicker #dp
+                  startView="multi-year"
+                  (yearSelected)="chosenYearHandler($event)"
+                  (monthSelected)="chosenMonthHandler($event, dp)"
+                  panelClass="example-month-picker">
+  </mat-datepicker>
 </mat-form-field>

src/material-examples/datepicker-views-selection/datepicker-views-selection-example.ts

@@ -1,4 +1,4 @@
-import {Component} from '@angular/core';
+import {Component, ViewEncapsulation} from '@angular/core';
 import {FormControl} from '@angular/forms';
 import {MatDatepicker} from '@angular/material/datepicker';
 import {MomentDateAdapter} from '@angular/material-moment-adapter';
@@ -31,6 +31,7 @@ export const MY_FORMATS = {
   selector: 'datepicker-views-selection-example',
   templateUrl: 'datepicker-views-selection-example.html',
   styleUrls: ['datepicker-views-selection-example.css'],
+  encapsulation: ViewEncapsulation.None,
   providers: [
     // `MomentDateAdapter` can be automatically provided by importing `MomentDateModule` in your
     // application's root module. We provide it at the component level here, due to limitations of