Add support for Workflow Runs (#1583)

To build on the previous work supporting querying Workflows for GitHub
Actions, add a class and relevant methods to support querying runs of a
workflow.

github/WorkflowRun.pyi

@@ -0,0 +1,63 @@
+from datetime import datetime
+from typing import Any, Dict, NamedTuple, List
+
+from github.GitCommit import GitCommit
+from github.GithubObject import CompletableGithubObject
+from github.PullRequest import PullRequest
+from github.Repository import Repository
+
+class TimingData(NamedTuple):
+    billable: Dict[str, Dict[str, int]]
+    run_duration_ms: int
+
+class WorkflowRun(CompletableGithubObject):
+    def __repr__(self) -> str: ...
+    def _initAttributes(self) -> None: ...
+    def _useAttributes(self, attributes: Dict[str, Any]) -> None: ...
+    @property
+    def id(self) -> int: ...
+    @property
+    def head_branch(self) -> str: ...
+    @property
+    def head_sha(self) -> str: ...
+    @property
+    def run_number(self) -> int: ...
+    @property
+    def event(self) -> str: ...
+    @property
+    def status(self) -> str: ...
+    @property
+    def conclusion(self) -> str: ...
+    @property
+    def url(self) -> str: ...
+    @property
+    def html_url(self) -> str: ...
+    @property
+    def pull_requests(self) -> List[PullRequest]: ...
+    @property
+    def created_at(self) -> datetime: ...
+    @property
+    def updated_at(self) -> datetime: ...
+    @property
+    def jobs_url(self) -> str: ...
+    @property
+    def logs_url(self) -> str: ...
+    @property
+    def check_suite_url(self) -> str: ...
+    @property
+    def artifacts_url(self) -> str: ...
+    @property
+    def cancel_url(self) -> str: ...
+    @property
+    def rerun_url(self) -> str: ...
+    @property
+    def workflow_url(self) -> str: ...
+    @property
+    def head_commit(self) -> GitCommit: ...
+    @property
+    def repository(self) -> Repository: ...
+    @property
+    def head_repository(self) -> Repository: ...
+    def cancel(self) -> bool: ...
+    def rerun(self) -> bool: ...
+    def timing(self) -> TimingData: ...