inform users when they use python version which our current release(s) do no longer support

People struggle to `pip install --ugprade dandi` and alike to noavail due to use of older python versions (e.g. 3.8) which we no longer support.
I think it would be great if we could alert folks when they start `dandi` CLI using some elderly python which current version of dandi-cli no longer supports. But what would be the most efficient way to query pypi for list of version current `dandi` (and `dandi-schema`) supports? alternative would be to host somewhere that information here, or just parse e.g. like

```shell
curl --silent https://raw.githubusercontent.com/dandi/dandi-cli/refs/heads/master/setup.cfg | sed -n -e '/python_requires/s,.*>=,,p'
```
with some local caching to do that only once a week or so.