Escape rightly bash function

[Mte90]

This required a specific ticket for shellcheck #72
Doing some tests:

pub fun is_command(command: Text): Bool {
    if (unsafe $command -v "{command}" > /dev/null$) {
        return true
    }
    return false
}

Generate this bash:

function is_command__28_v0 {
    local command=$1
    [ -x "$(command -v ${command})" ];
    __AS=$?;
if [ $__AS != 0 ]; then
        __AF_is_command28_v0=0;
        return 0
fi
    __AF_is_command28_v0=1;
    return 0
}

For shellcheck it is wrong, it should be:

function is_command__28_v0 {
    local command=$1
    [ -x $(command -v "${command}") ];
    __AS=$?;
if [ $__AS != 0 ]; then
        __AF_is_command28_v0=0;
        return 0
fi
    __AF_is_command28_v0=1;
    return 0
}

Basically the change:

    [ -x "$(command -v ${command})" ]; //wrong
    [ -x $(command -v "${command}") ]; //right