Support ECharts `{@...}` templates

[kevinmarr]

The agent was trying to use these a lot w/ ECharts.

Eg.

option = {
  dataset: {
    dimensions: ['product', 'count', 'year'],
    source: [
      ['Matcha Latte', 89, 2024],
      ['Milk Tea', 92, 2024],
      ['Cheese Cocoa', 94, 2024]
    ]
  },
  series: [{
    type: 'bar',
    label: {
      show: true,
      // Using {@...} in a label
      formatter: 'Year: {@year}' 
    },
    tooltip: {
      // Using {@...} in a tooltip template
      formatter: 'Product: {@product} <br/> Sales: {@count} units'
    }
  }]
};

ECharts docs