#2861 Allow specify pending format for paragraph

[JiuqingSong]

In addition to pending segment format, we now support specify pending format for paragraph. To do that, assign a pending format object to context.newPendingParagraphFormat within callback of formatContentModel:

                    this.editor.formatContentModel((_, context) => {
                        context.newPendingParagraphFormat = {...};

                        return false;
                    });