switch workbench preferred color themes

Author: Shulammite-Aso

src/vs/gitpod/browser/workbench/workbench.ts

@@ -833,6 +833,8 @@ async function doStart(): Promise<IDisposable> {
 		},
 		configurationDefaults: {
 			'workbench.colorTheme': 'Gitpod Light',
+			'workbench.preferredLightColorTheme': 'Gitpod Light',
+			'workbench.preferredDarkColorTheme': 'Gitpod Dark',
 		},
 		developmentOptions: {
 			logLevel: logLevel ? parseLogLevel(logLevel) : undefined