[API] Add API for Dear ImGui v1.78

imgui-binding/src/main/java/imgui/flag/ImGuiButtonFlags.java

@@ -0,0 +1,20 @@
+package imgui.flag;
+
+public final class ImGuiButtonFlags {
+    private ImGuiButtonFlags() {
+    }
+
+    public static final int None = 0;
+    /**
+     * React on left mouse button (default).
+     */
+    public static final int MouseButtonLeft = 0;
+    /**
+     *  React on right mouse button.
+     */
+    public static final int MouseButtonRight = 1 << 1;
+    /**
+     * React on center mouse button.
+     */
+    public static final int MouseButtonMiddle = 1 << 2;
+}