Notify of new major versions available when running `gleam update`

[lpil]

Discussed in https://github.com/gleam-lang/gleam/discussions/3841

^{Originally posted by **hayleigh-dot-dev** November 17, 2024} As the ecosystem grows it is becoming more difficult to keep track of when packages are updated with new breaking changes. Short of just making a list of every dependency of every package I maintain and regularly checking for new versions, there is no real way to know if any of my dependencies have updated until a user opens an issue or I notice by happenstance. One thing I _can_ do reliably is run `gleam update` in my packages from time to time. I'd like to propose that command also reports when any major version bumps are available, something like: ``` % gleam deps update Resolving versions Downloading packages Downloaded 2 packages in 0.01s Hint: the following dependencies have new major versions available... - wibble@2 - wobble@3 ``` I think this would have a general benefit to the community: - package consumers get notified when things have moved on and can make an informed decision to upgrade or not. - package authors have an easier time broadcasting new changes, which is particularly impactful for "foundation" packages like `mist` or `lustre` where the community at large benefits from being on the same version. - package authors can more-easily make sure they're not fragmenting the community by sticking on old versions of dependencies unnecessarily.

[lpil]

Let's do it. I think Mix and Cargo have a nice way of displaying this