Homepage should provide options for files to load

[simonw]

I think https://lite.datasette.io/ should be an initial page that lets users select data - it shouldn't load Pyodide and Datasette directly.

That way I can provide a more user friendly UI than the current thing with the buttons in the footer.

I can also more easily expand it to cover additional options such as this one: https://observablehq.com/@simonw/open-every-csv-file-in-a-github-repository-in-datasette-lite

[simonw]

Loading options so far:

• URL to a CSV file
• URL to a SQLite database file
• URL to a SQL init script

To add:

• URL to a GitHub repository (can do this)
• URL to a public Google Sheet (can add /export?format=csv to it)
• A bunch of "try this example" links
• The ability to open your own CSV file (which goes to localStorage or maybe even window.showOpenFilePicker() on supporting browsers)
• URL to a JSON file. Would be neat if this worked directly with arrays and could be told which key to access for objects