done with imperative shell/ffi aspect of sending KEY_ESC to update thread when that action has occurred

ffi/glfw-input.c

@@ -6,6 +6,7 @@
 int PRESS = GLFW_PRESS;
 int REPEAT = GLFW_REPEAT;
 int RELEASE = GLFW_RELEASE;
+int KEY_ESC = GLFW_KEY_ESCAPE;
 
 void framebufferSizeCallback(GLFWwindow* window, int width, int height) {
   glViewport(0, 0, width, height);
@@ -24,3 +25,11 @@ void setCharCallback(GLFWwindow* window) {
   glfwSetCharCallback(window, charCallback);
 }
 
+void keyCallback(GLFWwindow *window, int key, int scancode, int action, int mods) {
+  mltonKeyCallback(key, scancode, action, mods);
+}
+
+void setKeyCallback(GLFWwindow *window) {
+  glfwSetKeyCallback(window, keyCallback);
+}
+