array_map<char, bool> compiles error.

code:
```
tsl::array_map<char, bool> m;
m["abc"] = false;
```
compiles error:
```
array-hash/include/tsl/array_hash.h:1230:14: error: non-const lvalue reference to type 'bool' cannot bind to a temporary of type 'std::vector<bool>::reference' (aka '__bit_reference<std::vector<bool>>')
      return this->m_values[it_find.first.value()];
```
std::vector<bool> is specialized