Incorect usage of glfw key callback on unknown keys

[Edouard127]

The current implementation for mapping key codes to enums is incorrect as keys not supported on the current platform will return -1 when pressed.
For a concrete example, when a user scrolls a volume knob but the keyboard doesn't have volume keys, glfw will interpret these keys as unknown

The glfw doc states:

If the specified [key token](@ref keys) corresponds to a physical key not
supported on the current platform then this method will return `-1`.

The fix is as simple as adding a Unknown enum (see glfw/glfw#1076)

(the following crash was triggered by scrolling my volume knob on my headset)
Thread backtrace:

"main@1" prio=5 tid=0x1 nid=NA runnable
  java.lang.Thread.State: RUNNABLE
	  at uno.glfw.Key$Companion.of(_Arrays.kt:1110)
	  at uno.glfw.GlfwWindow._set_keyCB_$lambda$26$lambda$25(GlfwWindow.kt:415)
	  at uno.glfw.GlfwWindow$$Lambda/0x00000297950861f8.invoke(Unknown Source:-1)
	  at org.lwjgl.glfw.GLFWKeyCallbackI.callback(GLFWKeyCallbackI.java:44)
	  at org.lwjgl.system.JNI.callPPPPP(JNI.java:-1)
	  at org.lwjgl.system.windows.User32.nCallWindowProc(User32.java:1301)
	  at imgui.windowsIme.imeListener.invoke(imeListener.kt:179)
	  at org.lwjgl.system.windows.WindowProcI.callback(WindowProcI.java:43)
	  at org.lwjgl.system.JNI.invokeV(JNI.java:-1)
	  at org.lwjgl.glfw.GLFW.glfwPollEvents(GLFW.java:3438)
	  at uno.glfw.glfw.pollEvents(glfw.kt:260)
	  at com.lambda.ImGuiKt.main(GlfwWindow.kt:515)
	  at com.lambda.ImGuiKt.main(Unknown Source:-1)

Concerned frame:

first:1110, Key$Companion (uno.glfw)
of:141, Key$Companion (uno.glfw)
12 hidden frames
main:107, ImGuiKt (com.lambda)

this = {Key$Companion@2798} uno.glfw.Key$Companion@e67a8e0
Exception = {NoSuchElementException@2796} 
 backtrace = {Object[7]@4049} 
 detailMessage = "Array contains no element matching the predicate."
 cause = {NoSuchElementException@2796} "java.util.NoSuchElementException: Array contains no element matching the predicate."
 stackTrace = {StackTraceElement[12]@4054} 
 depth = 12
 suppressedExceptions = {Collections$EmptyList@4052}  size = 0
i = -1

glfw callback frame:

it = {ImplGlfw$Companion$keyCB$1@3147} (uno.glfw.GlfwWindow, uno.glfw.Key, kotlin.Int, uno.glfw.InputAction, kotlin.Int) -> kotlin.Unit
action = 1
key = -1
mods = 0
scanCode = 256
wnd = 2850039680800