Add Secret and Variable classes (#2623)

Co-authored-by: Enrico Minack <github@enrico.minack.dev>

github/Repository.pyi

@@ -57,6 +57,7 @@ from github.RepositoryAdvisoryVulnerability import (
 )
 from github.RepositoryKey import RepositoryKey
 from github.RepositoryPreferences import RepositoryPreferences
+from github.Secret import Secret
 from github.SelfHostedActionsRunner import SelfHostedActionsRunner
 from github.SourceImport import SourceImport
 from github.Stargazer import Stargazer
@@ -67,6 +68,7 @@ from github.StatsParticipation import StatsParticipation
 from github.StatsPunchCard import StatsPunchCard
 from github.Tag import Tag
 from github.Team import Team
+from github.Variable import Variable
 from github.View import View
 from github.Workflow import Workflow
 from github.WorkflowRun import WorkflowRun
@@ -282,9 +284,12 @@ class Repository(CompletableGithubObject):
     def create_repository_dispatch(
         self, event_type: str, client_payload: Union[Dict[str, Any], _NotSetType] = ...
     ) -> bool: ...
-    def create_secret(self, secret_name: str, unencrypted_value: str) -> bool: ...
-    def create_variable(self, variable_name: str, value: str) -> bool: ...
-    def update_variable(self, variable_name: str, value: str) -> bool: ...
+    def get_secrets(self) -> PaginatedList[Secret]: ...
+    def get_secret(self, secret_name: str) -> Secret: ...
+    def create_secret(self, secret_name: str, unencrypted_value: str) -> Secret: ...
+    def get_variables(self) -> PaginatedList[Variable]: ...
+    def get_variable(self, variable_name: str) -> Variable: ...
+    def create_variable(self, variable_name: str, value: str) -> Variable: ...
     def delete_secret(self, secret_name: str) -> bool: ...
     def delete_variable(self, variable_name: str) -> bool: ...
     def create_source_import(