option.alignment not works

Nobody has claimed this yet.

```
const sharedStructs = require('shared-structs'
,{ // option
alignment: {
foo: 1 // set the alignment of struct foo = 1, as in the description of options
}
});

const structs = sharedStructs('
#pragma pack(1) // request alignment=1, in source header file
struct foo {
uint8_t an_unsigned_num;
int32_t a_signed_num;
};
');
const test = structs.foo()
//console.log(test)
console.log(test.rawBuffer.length)
// error length != 5
```

Start by reproducing the supplied JavaScript example with the alignment option and the packed C-style struct definition. Trace how the alignment option and #pragma pack(1) affect the generated foo layout, then verify that test.rawBuffer.length is 5 for the example.

Written by the indexing model from the issue text.