cImporting dynlib doesn't add #include header in generated C code
When I'm just cImport:ing a header it gets included in the generated C code like this:
```nim
# in Nim code
cImport("include/header1.h")
```
```c
// in C code
#include "path to header1.h"
```
But when I give it a dynamic library it doesn't include it in the generated C code:

```nim
# in Nim code
cImport("include/header1.h")
cImport("include/header2.h", "dynlib2")
```
```c
// generated C 
#include "path to header1.h"
```
```c
// expected C
#include "path to header1.h"
#include "path to header2.h"
```
This is troublesome if  `header2.h` contains type definitions that is needed for the program. I solved this by moving the type definitions to a separate header file but it would be nice if Nimterop did this automagically in some way for me. Is there a reason why the header file doesn't get included or is it me who are just missing something 😅 