[API] Implement binding for ImGui::getWindowScrollbarRect (#81)

* Implemented binding for ImGui::getWindowScrollbarRect

* checkstyle fixes

* more logic naming for boolean fields in ImGuiWindow struct

Co-authored-by: aleksandr.cayun <aleksandr.cayun@vizor-games.com>

imgui-binding/src/main/java/imgui/internal/ImGuiWindow.java

@@ -0,0 +1,31 @@
+package imgui.internal;
+
+import imgui.binding.ImGuiStruct;
+
+public class ImGuiWindow extends ImGuiStruct {
+    public ImGuiWindow(final long ptr) {
+        super(ptr);
+    }
+
+    /*JNI
+        #include "_common.h"
+        #include <imgui_internal.h>
+
+        #define IMGUI_WINDOW ((ImGuiWindow*)STRUCT_PTR)
+     */
+
+    /**
+     * Is scrollbar visible?
+     */
+    public native boolean isScrollbarX(); /*
+       return IMGUI_WINDOW->ScrollbarX;
+    */
+
+    /**
+     * Is scrollbar visible?
+     */
+    public native boolean isScrollbarY(); /*
+       return IMGUI_WINDOW->ScrollbarY;
+    */
+
+}