add imgui

libs/imgui/examples/example_allegro5/imconfig_allegro5.h

@@ -0,0 +1,11 @@
+//-----------------------------------------------------------------------------
+// COMPILE-TIME OPTIONS FOR DEAR IMGUI ALLEGRO 5 EXAMPLE
+// See imconfig.h for the full template
+// Because Allegro doesn't support 16-bit vertex indices, we enable the compile-time option of imgui to use 32-bit indices
+//-----------------------------------------------------------------------------
+
+#pragma once
+
+// Use 32-bit vertex indices because Allegro doesn't support 16-bit ones
+// This allows us to avoid converting vertices format at runtime
+#define ImDrawIdx  int