Feature Request: Support using ASDF `.tool-versions` file for setting the bun version

[jtannas]

ASDF is a tool for managing language versions in a project, and it uses a .tool-versions file for managing which language version should be in use.
It has a plugin for it for managing the bun version.

I'd really like if I could tell the setup-bun action to use the same bun version as the ASDF .tool-versions file.

This feature is available in similar setup-<lang> actions.
eg.

• automatic version file detection in setup-ruby
• node-version-file as an option in setup-node