Add Num Lock and Caps Lock modifier from GLFW

# Summary of feature
I have found something that Silk.NET does not implement for GLFW.
https://www.glfw.org/docs/3.3/group__mods.html

and possibly this function:
https://www.glfw.org/docs/3.3/group__input.html#gaa92336e173da9c8834558b54ee80563b

tested on Silk.NET 2.22.0 GLFW 3.4.0

specifically the ones that are missing are:
```C
GLFW_MOD_CAPS_LOCK 0x0010
GLFW_MOD_NUM_LOCK 0x0020
```

what Silk.NET has:
```C#
namespace Silk.NET.GLFW
{
///
/// Key modifiers, such as Shift or CTRL.
///
public enum KeyModifiers
{
///
/// if one or more Shift keys were held down.
///
Shift = 0x0001,

///
/// If one or more Control keys were held down.
///
Control = 0x0002,

///
/// If one or more Alt keys were held down.
///
Alt = 0x0004,

///
/// If one or more Super keys were held down.
///
Super = 0x0008
}
}
```

# Comments
Related issue on GLFW:
https://github.com/glfw/glfw/issues/946

# Does this have a proposal?
no