rename local `stack` to `stackCfg` to eliminate `exports.`
rename local `stack` to `stackCfg` to eliminate `exports.`

uwdata/vega-lite,vega/vega-lite,vega/vega-lite,uwdata/vega-lite,uwdata/vega-lite,vega/vega-lite,vega/vega-lite,uwdata/vega-lite,uwdata/vega-lite,vega/vega-lite