exp-enable chat.implicitContext.enabled (microsoft#298317)

* chat: mark implicitContext.enabled as experiment-configurable

* chat: tag implicitContext.enabled as experimental

Author: daviddossett

src/vs/workbench/contrib/chat/browser/chat.contribution.ts

@@ -265,6 +265,10 @@ configurationRegistry.registerConfiguration({
 			},
 			default: {
 				'panel': 'always',
+			},
+			tags: ['experimental'],
+			experiment: {
+				mode: 'startup'
 			}
 		},
 		'chat.implicitContext.suggestedContext': {