Add new `Label` model.

[BURG3R5]

In this issue, you'll add a new model class Label and a new member label to the GitHubEvent class.

Step 1

Create new model class

For this step, you'll add a new model class Label in the folder bot/models/github/

First you'll create a new file in the folder, and name it label.py

Inside that file, you'll create a class called Label. This class will have two members: name and action. Both variables will be of the type str. You can refer to the Repository model for guidance.

Step 2

Update GitHubEvent model

For this step, you'll add a member to the GitHubEvent model present in the file bot/models/github/event.py

First you'll add a line below the line reviewers: Optional[list[User]] that declares a variable label with type Optional[Label].

Next you'll add an if statement below the line self.reviewers = kwargs["reviewers"] that confirms if there is a key "label" in the dictionary kwargs. If that is true, then you should assign kwargs["label"] to self.label.

This issue is a part of a bigger issue (#6). Leave a comment if you have any doubts.