Rename package: enums->flag

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

@@ -0,0 +1,15 @@
+package imgui.flag;
+
+/**
+ * Identify a mouse button.
+ * Those values are guaranteed to be stable and we frequently use 0/1 directly. Named enums provided for convenience.
+ */
+public final class ImGuiMouseButton {
+    private ImGuiMouseButton() {
+    }
+
+    public static final int Left = 0;
+    public static final int Right = 1;
+    public static final int Middle = 2;
+    public static final int COUNT = 5;
+}