Make it easier to create a new file:

current:

```cpp
auto file = File(File::IsOverwrite::yes, "file.txt");
```

perhaps:

```cpp
auto file = File::create("file.txt");
static File create(var::StringView name, File::IsOverwrite is_overwrite = File::IsOverwrite::yes){
  return File(is_overwrite, name);
}
```