Recommend users to not use the country and territory autocomplete

[owenatgov]

Changes

1. Adds a note to the top of the readme Restructures the readme, advising users to not use this repo and the reasons why
2. Remove the 'Keep the data up to date' section as it's no longer true

Notes

The second change is possibly the slgihtly more controversial one. It means teams now have no assurance that the data is kept up to date (which unfortunately is closer to the truth) however this section doesn't really hold any value besides the untrue statements. The 2 platforms suggested for keeping up to date are both dead projects. I'm however less confident in this change compared to the first change. I'm interested in folk's opinions or if we should leave it or just morph the content a bit.

[querkmachine]

Should we add advice on what to use instead?

For example, suggesting to use Accessible Autocomplete with FCDO's geographical names index as a data source?

[owenatgov]

@querkmachine I did think about adding a line like "the team will look at alternatives in the future". Maybe I can put that example in so folks have something but try to qualify it that this isn't a complete alternative. Probably the team need to discuss where to point people and agree, although I can't think of anything better than what you've suggested.

[romaricpascal]

For example, suggesting to use Accessible Autocomplete with FCDO's geographical names index as a data source?

Pointing people to the FCDO list with the caveat that people need to double check that it's suitable for their own project sounds nice to do. It's also something we can easily amend if people come up with better sources.

[owenatgov]

I've added a note on the FCDO datasource. I'm not super confident about the content so I'd appreciate a review.

[calvin-lau-sig7]

I've made a new commit that includes an edit of the latest message, and restructures the headings to make it fit better.