Cannot compile sample project with nuklear

Hi there,

ich have an annoying issue with compiling the sample project, which I canot get rid of. My project structure looks like this:

with the ```nuklear``` directory being the freshly downloaded and extracted copy of the nuklear repository.

the ```CMakeLists.txt``` is:

```
cmake_minimum_required(VERSION 3.20)
project(nuklearTest)

set(CMAKE_CXX_STANDARD 14)

add_executable(nuklearTest main.cpp)

target_include_directories(${PROJECT_NAME} PUBLIC ${PROJECT_SOURCE_DIR}/nuklear)
```

here's my main.cpp:

```
#include
#include "nuklear.h"

int main()
{
/* init gui state */
struct nk_context ctx;
nk_init_fixed(&ctx, calloc(1, MAX_MEMORY), MAX_MEMORY, &font);

enum {EASY, HARD};
static int op = EASY;
static float value = 0.6f;
static int i = 20;

if (nk_begin(&ctx, "Show", nk_rect(50, 50, 220, 220),
NK_WINDOW_BORDER|NK_WINDOW_MOVABLE|NK_WINDOW_CLOSABLE)) {
/* fixed widget pixel width */
nk_layout_row_static(&ctx, 30, 80, 1);
if (nk_button_label(&ctx, "button")) {
/* event handling */
}

/* fixed widget window ratio width */
nk_layout_row_dynamic(&ctx, 30, 2);
if (nk_option_label(&ctx, "easy", op == EASY)) op = EASY;
if (nk_option_label(&ctx, "hard", op == HARD)) op = HARD;

/* custom widget pixel width */
nk_layout_row_begin(&ctx, NK_STATIC, 30, 2);
{
nk_layout_row_push(&ctx, 50);
nk_label(&ctx, "Volume:", NK_TEXT_LEFT);
nk_layout_row_push(&ctx, 110);
nk_slider_float(&ctx, 0, &value, 1.0f, 0.1f);
}
nk_layout_row_end(&ctx);
}
nk_end(&ctx);

}
```

First, I am missing references to the constant MAX_MEMORY and &font. I have manually created them at the beginning of the main.cpp function like this (I don't know if that's correct, but at least the CLion IDE doesn't complain anymore):
```
const int MAX_MEMORY = 128;
nk_user_font font = (const nk_user_font&)"Times New Roman";
```

but now I encounter the error:

```main.cpp.obj : error LNK2019: unresolved external symbol nk_init_fixed referenced in function main
main.cpp.obj : error LNK2019: unresolved external symbol nk_begin referenced in function main
main.cpp.obj : error LNK2019: unresolved external symbol nk_end referenced in function main
main.cpp.obj : error LNK2019: unresolved external symbol nk_layout_row_dynamic referenced in function main
main.cpp.obj : error LNK2019: unresolved external symbol nk_layout_row_static referenced in function main
main.cpp.obj : error LNK2019: unresolved external symbol nk_layout_row_begin referenced in function main
main.cpp.obj : error LNK2019: unresolved external symbol nk_layout_row_push referenced in function main
main.cpp.obj : error LNK2019: unresolved external symbol nk_layout_row_end referenced in function main
main.cpp.obj : error LNK2019: unresolved external symbol nk_label referenced in function main
main.cpp.obj : error LNK2019: unresolved external symbol nk_button_label referenced in function main
main.cpp.obj : error LNK2019: unresolved external symbol nk_option_label referenced in function main
main.cpp.obj : error LNK2019: unresolved external symbol nk_slider_float referenced in function main
main.cpp.obj : error LNK2019: unresolved external symbol nk_rect referenced in function main
nuklearTest.exe : fatal error LNK1120: 13 unresolved externals
```

I am quite sure the ```nuklear.h``` is correctly linked, as I can implement other functions from within the IDE. I already played around with other CMake commands, like ```include_directories``` in order to find nuklear, but to no avail. I have also tried to include:

```
#define NK_IMPLEMENTATION
#include "nuklear.h"
```

Then, the project compiles but I get this error during execution:


There must be something I am missing. Any help is welcome. Thanks

Reproduce the sample using CMakeLists.txt and main.cpp, then inspect how nuklear.h is included and built. Compare the linker errors with the NK_IMPLEMENTATION attempt and investigate the reported runtime failure; done means the sample builds and runs without those errors.

Written by the indexing model from the issue text.