fix(module:button): add ant-btn-default class (#8501)

Author: HyperLife1119

components/button/button.component.ts

@@ -22,7 +22,7 @@ import {
   SimpleChanges,
   ViewEncapsulation
 } from '@angular/core';
-import { fromEvent, Subject } from 'rxjs';
+import { Subject, fromEvent } from 'rxjs';
 import { filter, startWith, takeUntil } from 'rxjs/operators';
 
 import { NzConfigKey, NzConfigService, WithConfig } from 'ng-zorro-antd/core/config';
@@ -50,6 +50,7 @@ const NZ_CONFIG_MODULE_NAME: NzConfigKey = 'button';
   `,
   host: {
     class: 'ant-btn',
+    '[class.ant-btn-default]': `nzType === 'default'`,
     '[class.ant-btn-primary]': `nzType === 'primary'`,
     '[class.ant-btn-dashed]': `nzType === 'dashed'`,
     '[class.ant-btn-link]': `nzType === 'link'`,

components/button/button.spec.ts

@@ -1,6 +1,6 @@
 import { BidiModule, Dir } from '@angular/cdk/bidi';
 import { ApplicationRef, Component, Input, OnInit, ViewChild } from '@angular/core';
-import { fakeAsync, TestBed, tick } from '@angular/core/testing';
+import { TestBed, fakeAsync, tick } from '@angular/core/testing';
 import { By } from '@angular/platform-browser';
 
 import { ɵComponentBed as ComponentBed, ɵcreateComponentBed as createComponentBed } from 'ng-zorro-antd/core/testing';
@@ -51,6 +51,9 @@ describe('button', () => {
       expect(buttonElement.classList).toContain('ant-btn-block');
     });
     it('should apply classname based on nzType', () => {
+      testBed.component.nzType = 'default';
+      testBed.fixture.detectChanges();
+      expect(buttonElement.classList).toContain('ant-btn-default');
       testBed.component.nzType = 'primary';
       testBed.fixture.detectChanges();
       expect(buttonElement.classList).toContain('ant-btn-primary');