通过监听siyuan.editorIsFullscreen对象变化判断是否全屏

// 定义一个可观察的属性
window.siyuan._editorIsFullscreen = window.siyuan.editorIsFullscreen || false;
Object.defineProperty(window.siyuan, 'editorIsFullscreen', {
    get: function() {
        return this._editorIsFullscreen;
    },
    set: function(value) {
        const oldValue = this._editorIsFullscreen;
        this._editorIsFullscreen = value;
        // value true是全屏，false是退出全屏
        console.log(`editorIsFullscreen changed from ${oldValue} to ${value}`);
    },
    configurable: true,
    enumerable: true
});