Record the shell used for each command

I would find it useful if atuin recorded the shell used for each command.

For various reasons, I occasionally switch between shells for different purposes, and sometimes a command that works in one shell (bash/zsh) doesn't work in another (fish). This is even more of an issue if atuin grows to support more of the exotic shells (nushell, elvish, etc).

Having the ability to know which shell was used for a command would let me filter by commands for the current shell environment.