chore(editor): add edgeless scribbled style feature flag (#11127)

Closes: [BS-2805](https://linear.app/affine-design/issue/BS-2805/下掉线条样式切换功能，需添加-feature-flag)

blocksuite/affine/gfx/connector/src/toolbar/config.ts

@@ -209,8 +209,7 @@ export const connectorToolbarConfig = {
     },
     {
       id: 'b.style',
-      // TODO(@fundon): should add a feature flag
-      when: false,
+      when: ctx => ctx.features.getFlag('enable_edgeless_scribbled_style'),
       content(ctx) {
         const models = ctx.getSurfaceModelsByType(ConnectorElementModel);
         if (!models.length) return null;