Add support for deployment statuses (#1588)

* Added DeploymentStatus class
* Added stubs for DeploymentStatus class
* Fixed headers for DeploymentStatus.py
* Added get/list/create deployment status methods
* Added DeploymentStatus repr
* Added attribute check tests for DeploymentStatus
* Added "create deployment status" test
* Added test for Deployment.get_statuses()
* Added Deployment.get_status() method

Fixes #1586

github/DeploymentStatus.pyi

@@ -0,0 +1,35 @@
+from datetime import datetime
+from typing import Any, Dict
+
+from github.GithubObject import CompletableGithubObject
+from github.NamedUser import NamedUser
+
+
+class DeploymentStatus(CompletableGithubObject):
+    def __repr__(self) -> str: ...
+    def _initAttributes(self) -> None: ...
+    def _useAttributes(self, attributes: Dict[str, Any]) -> None: ...
+    @property
+    def created_at(self) -> datetime: ...
+    @property
+    def creator(self) -> NamedUser: ...
+    @property
+    def deployment_url(self) -> str: ...
+    @property
+    def description(self) -> str: ...
+    @property
+    def environment(self) -> str: ...
+    @property
+    def repository_url(self) -> str: ...
+    @property
+    def state(self) -> str: ...
+    @property
+    def target_url(self) -> str: ...
+    @property
+    def updated_at(self) -> datetime: ...
+    @property
+    def url(self) -> str: ...
+    @property
+    def id(self) -> int: ...
+    @property
+    def node_id(self) -> str: ...