fix: add clone methods to GuildMember and GuildMemberRoleStore

Fixes #2312
This adds clone method to both classes to achieve the expected behaviour when cloning a GuildMember, also cloning their roles store

src/stores/GuildMemberRoleStore.js

@@ -128,6 +128,12 @@ class GuildMemberRoleStore extends DataStore {
     }
   }
 
+  clone() {
+    const clone = new this.constructor(this.member);
+    clone._patch(this.keyArray());
+    return clone;
+  }
+
   /**
    * Resolves a RoleResolvable to a Role object.
    * @method resolve

src/structures/GuildMember.js

@@ -75,6 +75,12 @@ class GuildMember extends Base {
     if (data.roles) this.roles._patch(data.roles);
   }
 
+  _clone() {
+    const clone = super._clone();
+    clone.roles = this.roles.clone();
+    return clone;
+  }
+
   get voiceState() {
     return this._frozenVoiceState || this.guild.voiceStates.get(this.id) || {};
   }