images: add index to key function
images: add index to key function

- so that multiple images can share the same source field

plotly/plotly.js,plotly/plotly.js,plotly/plotly.js,iongroup/plotly.js,aburato/plotly.js,etpinard/plotly.js,iongroup/plotly.js,asolagmbh/plotly.js,etpinard/plotly.js,asolagmbh/plotly.js,iongroup/plotly.js,aburato/plotly.js,etpinard/plotly.js,plotly/plotly.js,asolagmbh/plotly.js