This is a new pull request that replaces original pull request

• Add flag to set the shell to be used for the the input command

This is in response to issue #141
Adds support to set the shell to be used with input-cmd. Fixes some issues that happen when using the default shell (/bin/sh). But still defaults to current shell if not set.

For example:
echo does not support -n flag in /bin/sh

Being able to set /bin/zsh or /bin/bash would fix the issue.

Usage:

ffuf -v \
    -input-shell "/bin/zsh" \
    -input-cmd 'echo -n subscriptions' \
    -input-num 1 -u https://example.com/path1/FUZZ