feat(buttons): add aria-attributes (#4082)

Closes #4068

Author: tarusin

demo/src/app/components/+buttons/demos/custom-checkbox-value/custom-checkbox-value.ts

@@ -5,5 +5,5 @@ import { Component } from '@angular/core';
   templateUrl: './custom-checkbox-value.html'
 })
 export class DemoButtonsCustomCheckboxValueComponent {
-  singleModel: string = '1';
+  singleModel = '1';
 }

demo/src/ng-api-doc.ts

@@ -151,13 +151,13 @@ export const ngdoc: any = {
       {
         "name": "btnCheckboxFalse",
         "defaultValue": "false",
-        "type": "any",
+        "type": "boolean",
         "description": "<p>Falsy value, will be set to ngModel </p>\n"
       },
       {
         "name": "btnCheckboxTrue",
         "defaultValue": "true",
-        "type": "any",
+        "type": "boolean",
         "description": "<p>Truthy value, will be set to ngModel </p>\n"
       }
     ],

src/buttons/button-checkbox.directive.ts

@@ -30,7 +30,9 @@ export class ButtonCheckboxDirective implements ControlValueAccessor, OnInit {
   /** Falsy value, will be set to ngModel */
   @Input() btnCheckboxFalse: any = false;
 
-  @HostBinding('class.active') state = false;
+  @HostBinding('class.active')
+  @HostBinding('attr.aria-pressed')
+  state = false;
 
   protected value: any;
   protected isDisabled: boolean;

src/buttons/button-radio.directive.ts

@@ -54,6 +54,7 @@ export class ButtonRadioDirective implements ControlValueAccessor, OnInit {
   }
 
   @HostBinding('class.active')
+  @HostBinding('attr.aria-pressed')
   get isActive(): boolean {
     return this.btnRadio === this.value;
   }