Add support for mise for dependency management

What does this MR do and why?

I'm noticing that more and more, folks are switching to mise (https://mise.jdx.dev) for dependency management over asdf:

• gitlab-org/gitlab-development-kit#1683
• gitlab-com/runbooks#134

While I don't think we need to move off asdf ourselves, I want to reduce barriers to contributing to this project. Because mise uses a lot of asdf things (including plugins and supporting .tool-versions), it's very easy to support as an alternative and asdf users won't notice a difference.

Eventually, we might make "automated dependency management" optional, so folks can use whatever they want as long as the project can reach the binaries.

For now, we'll have an SSoT of dependencies and versions, and two supported ways of managing them.

How to set up and validate locally

1. Configure a local GitLab Docs environment: https://gitlab.com/gitlab-org/technical-writing-group/gitlab-docs-hugo/-/blob/main/doc/setup.md.
2. Check out this branch.
3. Run make setup. Your existing asdf installation is unaffected.
4. Optional. Tear down asdf: https://asdf-vm.com/manage/core.html#uninstall.
5. Optional. Install mise: https://mise.jdx.dev/getting-started.html.
6. Optional. Run make setup. Your dependencies are installed using mise.
7. Optional. Run make view. You can build and preview the site.

Merge request acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this merge request.