Stable documentation refers to latest demo instance

[sebbacon]

The docs have lots of examples that point to the http://latest.datasette.io/ demo instance. This is deployed from main on every push.

The domain is hardcoded in the structured text, with the result that the default (stable) branch documentation points to a deploy of a different branch. This means the examples aren't guaranteed to work. ¹

I suppose the answer is to build and deploy a stable.datasette.io in addition to the build off main, and interpolate that into the docs. However, I appreciate that's quite a lot of work; I'm afraid I've run out of steam having just thrown the PR "fix" away.

So just leaving this here as a marker to maybe come back to. Perhaps there are some lower-effort mitigations I've not thought of.

Footnotes

1. This contributed to me getting in quite a muddle in Canned queries don't appear in the app #2325: I'd managed to deploy a latest branch when making a PR, which also happend to break my canned queries config, because of this change. As a safety check I referred to the docs, and noted that the examples there were also broken, confirming my (incorrect) hypothesis that it was broken in main -- when in fact, the docs in main are correct! Meanwhile I wrote a new PR to "fix" the "broken" config... ↩