echarts添加文字水印，在option里添加graphic即可，详细代码如下所示：

option={{
                            toolbox: {
                                feature: {
                                    dataZoom: {
                                        yAxisIndex: 'none',
                                    },
                                    restore: {},
                                    saveAsImage: {},
                                },
                            },
                            xAxis: {
                                type: 'time',
                            },
                            yAxis: {
                                type: 'value',
                            },
                            graphic: [
                                {
                                        type: 'group',
                                        // rotation: Math.PI / 2,
                                        bounding: 'raw',
                                        right:200,
                                        top: 40,
                                        z: 100,
                                        children: [
                                                {
                                                        type: 'text',
                                                        left: 'center',
                                                        top: 'center',
                                                        z: 100,
                                                        style: {
                                                                fill: '#cccccc',
                                                                text: `想添加的文字水印`,
                                                                font: 'bold 16px sans-serif'
                                                        }
                                                }
                                        ]
                                },],
}}