feat: export setStageSize redux action

This will allow us to override the default stage size or change the stage size
from outside of the GUI component.

Author: sebjacobs

packages/scratch-gui/src/exported-reducers.ts

@@ -18,6 +18,7 @@ import {
     closeLoadingProject,
     openTelemetryModal
 } from './reducers/modals.js';
+import {setStageSize} from './reducers/stage-size';
 
 export const guiReducers = {
     locales: LocalesReducer,
@@ -34,6 +35,7 @@ export {
     requestNewProject,
     requestProjectUpload,
     setProjectId,
+    setStageSize,
 
     openLoadingProject,
     closeLoadingProject,