docs(aio): Update NgStyle and NgClass to use quoted keys

aio/content/examples/template-syntax/src/app/app.component.html

@@ -161,7 +161,7 @@
   <!-- #docregion property-binding-syntax-1 -->
   <img [src]="heroImageUrl">
   <hero-detail [hero]="currentHero"></hero-detail>
-  <div [ngClass]="{special: isSpecial}"></div>
+  <div [ngClass]="{'special': isSpecial}"></div>
   <!-- #enddocregion property-binding-syntax-1 -->
 </div>
 <br><br>
@@ -496,7 +496,7 @@ bindon-ngModel
 <div [ngClass]="isSpecial ? 'special' : ''">This div is special</div>
 
 <div class="bad curly special">Bad curly special</div>
-<div [ngClass]="{bad:false, curly:true, special:true}">Curly special</div>
+<div [ngClass]="{'bad':false, 'curly':true, 'special':true}">Curly special</div>
 
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aio/content/examples/template-syntax/src/app/app.component.ts

@@ -140,9 +140,9 @@ export class AppComponent implements AfterViewInit, OnInit {
   setCurrentClasses() {
     // CSS classes: added/removed per current state of component properties
     this.currentClasses =  {
-      saveable: this.canSave,
-      modified: !this.isUnchanged,
-      special:  this.isSpecial
+      'saveable': this.canSave,
+      'modified': !this.isUnchanged,
+      'special':  this.isSpecial
     };
   }
   // #enddocregion setClasses