Add ImGuiOnceUponAFrame helper

imgui-binding/src/main/java/imgui/ImGuiOnceUponAFrame.java

@@ -0,0 +1,23 @@
+package imgui;
+
+/**
+ * Helper: Execute a block of code at maximum once a frame.
+ * Convenient if you want to quickly create an UI within deep-nested code that runs multiple times every frame.
+ * Usage: static ImGuiOnceUponAFrame oaf; if (oaf) ImGui::Text("This will be called only once per frame");
+ * <p>
+ * BINDING NOTICE:
+ * Java example: if (ImGuiOnceUponAFrame.get()) ImGui.text("This will be called only once per frame");
+ */
+public final class ImGuiOnceUponAFrame {
+    private ImGuiOnceUponAFrame() {
+    }
+
+    /*JNI
+        #include <imgui.h>
+     */
+
+    public static native boolean get(); /*
+        ImGuiOnceUponAFrame oaf;
+        return (bool)oaf;
+    */
+}