We currently have at least 3 different variants of index.html:

• web_viewer/index.html is the version that gets served on app.rerun.io
• web_viewer/index_bundled is the version that gets served directly from the viewer
• scripts/demo_assets/templates/example.hml is the version that gets served on the demo page

Making functional changes to the web-app that touch the index.html involves touching all 3 of these files while tracking slight modifications.

See #2421 for motivation.