extend_right/left() needs char const * overload.

[h-2]

extend_right() in the index module does not handle null-terminated strings properly:

#include <seqan3/search/fm_index/all.hpp>
#include <seqan3/core/debug_stream.hpp>

using namespace seqan3;

int main()
{
std::string text = "How much wood would a woodchuck chuck?";
fm_index index{text};

auto it = index.begin();

if (it.extend_right("wood"))
    debug_stream << it.locate() << '\n';
}

Outputs no results, but wrapping "wood" into std::string produces correct behaviour.