Switch from rbenv/nodenv to adsf

[dhh]

One unified solution to it all.

[jeffreyguenther]

You might find that mise is a better option than asdf. mise can leverage the asdf plugin ecosystem, but has its own opinions on a few things. More importantly, mise is fast. It's not uncommon to get timeout issues with prompts like Starship with asdf.

It's worth checking out.

[taranjlu]

Definitely +1 for mise. It is much faster and does not have the issues with shims that can cause asdf to break.

[nickmccullum]

Another +1 for mise.

[pepicrft]

And another one here! @jdxcode has done an amazing job there in terms of DX.
I was also thinking that we could add support of Ruby as a backend so that people can install Ruby gems easily by just running:

mise install gem:rails@latest

[dhh]

Work in #36. Soliciting opinions on the transition there.