allow Contact.remark(null) to delete remark

src/contact.ts

@@ -21,7 +21,7 @@ type ContactObj = {
   id:         string
   name:       string
   province:   string
-  remark:     string
+  remark:     string|null
   sex:        string
   signature:  string
   star:       boolean
@@ -222,8 +222,12 @@ export class Contact implements Sayable {
    * set the remark for contact
    */
   public remark(newRemark: string): Promise<boolean>
+  /**
+   * delete the remark for a contact
+   */
+  public remark(empty: null): Promise<boolean>
 
-  public remark(newRemark?: string): Promise<boolean> | string {
+  public remark(newRemark?: string|null): Promise<boolean> | string {
     log.silly('Contact', 'remark(%s)', newRemark || '')
 
     if (newRemark === undefined) {

src/puppet-web/bridge.ts

@@ -134,7 +134,7 @@ export class Bridge {
     }
   }
 
-  public async contactRemark(contactId: string, remark: string): Promise<boolean> {
+  public async contactRemark(contactId: string, remark: string|null): Promise<boolean> {
     try {
       return await this.proxyWechaty('contactRemarkAsync', contactId, remark)
     } catch (e) {

src/puppet-web/puppet-web.ts

@@ -368,7 +368,7 @@ export class PuppetWeb extends Puppet {
     }
   }
 
-  public async contactRemark(contact: Contact, remark: string): Promise<boolean> {
+  public async contactRemark(contact: Contact, remark: string|null): Promise<boolean> {
     try {
       const ret = await this.bridge.contactRemark(contact.id, remark)
       if (!ret) {

src/puppet.ts

@@ -67,5 +67,5 @@ export abstract class Puppet extends EventEmitter implements Sayable {
    * Contact
    */
   public abstract contactFind(filterFunc: string): Promise<Contact[]>
-  public abstract contactRemark(contact: Contact, remark: string): Promise<boolean>
+  public abstract contactRemark(contact: Contact, remark: string|null): Promise<boolean>
 }