docs - line charts updates (#43845)

docs/data-modeling/model-persistence.md

docs/questions/images/goal-line.png

docs/questions/images/line-options.png

docs/questions/images/stacked-100.png

docs/questions/images/stacked-bar-chart.png

docs/questions/images/unpinned-from-zero-y-axis.png

...stions/sharing/visualizations/line-bar-and-area-charts.md