Customizing Axes
This bar chart displays the top 10 most populous countries in 2018, using data from the United Nations World Population Prospects. It shows how to customize D3 axes, including removing tick lines and the domain path, adding an axis label, and formatting population values using `d3.format` with a custom tick formatter that converts G to B. The visualization uses `d3.scaleLinear` for the x-axis, `d3.scaleBand` for the y-axis, and renders via SVG. Bars are filled with steelblue, and axis labels use custom CSS styling.