refactor: use user's shell instead of bash

[sudoAlphaX]

this patch allows one to use user's specified shell (from /etc/passwd) instead of bash in the video details (fzf).

I tried to make the script change $SHELL variable, but that meant the exported function generate_sha256 will not work.
I tried changing piping values into generate_sha256 to normal function calls, but i currently could not get it to work for the fzf and fzf preview commands.
Patches would be appreciated
Turns out i lost the changes

[Benexl]

Nice was wanting to use fish in the yt-x shell. I did some digging and found this way of getting the shell that launched the script otherwise your default shell. ps -o comm= -p "$PPID"
The other did not work on my end, mostly because fish is not my login shell and i only use it interactively.
Sth like this:

        user_shell="$(ps -o comm= -p "$PPID")"
        $user_shell -c "echo \"$init_text\""