SharePoint initialization people picker and add multiple peoples to SharePoint list.

In HTML require to have:

<script type="text/javascript" src="/_layouts/15/sp.runtime.js"></script>
<script type="text/javascript" src="/_layouts/15/sp.js"></script>
<script type="text/javascript" src="/_layouts/15/clienttemplates.js"></script>
<script type="text/javascript" src="/_layouts/15/clientforms.js"></script>
<script type="text/javascript" src="/_layouts/15/clientpeoplepicker.js"></script>
<script type="text/javascript" src="/_layouts/15/autofill.js"></script>

Additional funcation

Add user to PeoplePikcer:

key is 'domain\\loginName' or user mail
SPClientPeoplePicker.SPClientPeoplePickerDict['peoplePickerId'+"_TopSpan"].AddUserKeys(key);

To remove all users:

SPClientPeoplePicker.SPClientPeoplePickerDict['peoplePickerId'+"_TopSpan"].DeleteProcessedUser();

To prevent add multiple time the same user:

SPClientPeoplePicker.SPClientPeoplePickerDict[peoplePickerElementId + '_TopSpan'].OnUserResolvedClientScript = function (peoplePickerId, selectedUsersInfo){
  var users = selectedUsersInfo;
  for(var i = 0; i < users.length - 1; i++) if(users[users.length - 1].Key == users[i].Key) this.DeleteProcessedUser();
  };