Add ability to check diff without JS runtime

I tried to ask Claude to update my dependencies by asking it to run `mix hex.outdated` and checking the diff URL at the bottom of the output, read the changelog, etc. It wasn't able to do so because the diff is dynamically loaded. It would be great to have a URL like
```
https://diff.hex.pm/diff/<package_name>/<version1>..<version2>.patch
```