[Feature] 堆叠柱状图&堆叠条形图 totalLabl 期望支持 position

[webiamcome]

What problem does this feature solve?

在有负数的场景下，期望能根据总计值的正负来设置 position

spec:

const spec = {
  stack: true,
  data: [
    {
      name: 'allData',
      values: [
        {
          name: 'A',
          value: -12,
          group: '7+'
        },
        {
          name: 'B',
          value: -34,
          group: '7+'
        },
        {
          name: 'C',
          value: -25,
          group: '7+'
        },
        {
          name: 'D',
          value: -48,
          group: '7+'
        },
        {
          name: 'E',
          value: -55,
          group: '7+'
        },
        {
          name: 'F',
          value: -42,
          group: '7+'
        },
        {
          name: 'A',
          value: -23,
          group: '6-7'
        },
        {
          name: 'B',
          value: -25,
          group: '6-7'
        },
        {
          name: 'C',
          value: -18,
          group: '6-7'
        },
        {
          name: 'D',
          value: -19,
          group: '6-7'
        },
        {
          name: 'E',
          value: -15,
          group: '6-7'
        },
        {
          name: 'F',
          value: -12,
          group: '6-7'
        },
        {
          name: 'A',
          value: -31,
          group: '4-5'
        },
        {
          name: 'B',
          value: -33,
          group: '4-5'
        },
        {
          name: 'C',
          value: -4,
          group: '4-5'
        },
        {
          name: 'D',
          value: -24,
          group: '4-5'
        },
        {
          name: 'E',
          value: -18,
          group: '4-5'
        },
        {
          name: 'F',
          value: -2,
          group: '4-5'
        },
        {
          name: 'A',
          value: -56,
          group: '2-3'
        },
        {
          name: 'B',
          value: -29,
          group: '2-3'
        },
        {
          name: 'C',
          value: -15,
          group: '2-3'
        },
        {
          name: 'D',
          value: -1,
          group: '2-3'
        },
        {
          name: 'E',
          value: -14,
          group: '2-3'
        },
        {
          name: 'F',
          value: -16,
          group: '2-3'
        },
        {
          name: 'A',
          value: -15,
          group: '1'
        },
        {
          name: 'B',
          value: -11,
          group: '1'
        },
        {
          name: 'C',
          value: -15,
          group: '1'
        },
        {
          name: 'D',
          value: -2,
          group: '1'
        },
        {
          name: 'E',
          value: 0,
          group: '1'
        },
        {
          name: 'F',
          value: -5,
          group: '1'
        }
      ]
    }
  ],
  color: ['#009DB5', '#F0B71F', '#EB6F02', '#1E5273', '#3BA140'],
  totalLabel: {
    visible: true,
    position: 'bottom',
  },
  type: 'bar',
  xField: 'name',
  yField: 'value',
  seriesField: 'group',
  axes: [
    {
      orient: 'top',
    }
  ]
};

const vchart = new VChart(spec, { dom: CONTAINER_ID });
vchart.renderSync();

// Just for the convenience of console debugging, DO NOT COPY!
window['vchart'] = vchart;

What does the proposed API look like?

类似 label，函数场景下，datum 期望包含总计值

[xile611]

1.13.7支持了设置在底部