EGL generator doesn't provide runtime flags for extensions
I recently used GLAD for EGL (1.4) and required a couple extensions:
 - EGL_KHR_create_context
 - EGL_KHR_debug

Those particular extensions aren't very important but just used as an example. I was expecting things to work like GLAD for OpenGL where I can check the runtime extension flags to see if the device the app is running on supports them and augment behavior accordingly. So I expected the be able to do this:

```cpp
    if (GLAD_EGL_KHR_debug) { /* setup debug stuff */ }
```

But it seems that the glad_egl.h doesn't declare an extension variable for this purpose. Is this a bug or, for EGL, are users expected to do something else?

Thanks