This example displays the text "Hello D3" in the center of the page using a very large 13em font size. It demonstrates the most basic use of D3.js to manipulate the DOM, selecting the body element with `select` and setting its text content via `.text("Hello D3")`. The visualization relies on the D3 v6 library loaded from a CDN and the accompanying script is bundled in `bundle.js`. The page itself contains no charts or data, serving purely as a starting point for learning D3 conventions.