[feature] specify shell

[Rignchen]

the shell I use is nushell therefore it often happend that the syntaxe expected by termshot is not the same as the one used by nushell, I could solve it by adding nu -c at the beginning of my command but I like having the command visible and don't want the nu -c to appear on the image. I tried running it with interractive shell but I get wierd stuff on the image like duplicated command or autocomplete artefacts

would it be possible to have a flag like --shell which would tell termshot which shell to use for the screenshot?