Initial commit for GitHub migration based on spice2x-25-03-03

src/spice2x/overlay/imgui/extensions.h

@@ -0,0 +1,10 @@
+#pragma once
+
+namespace ImGui {
+
+    void HelpMarker(const char* desc);
+    void WarnMarker(const char* desc, const char* warn);
+    void DummyMarker();
+    void Knob(float fraction, float size, float thickness = 2.f,
+            float pos_x = -1.f, float pos_y = -1.f);
+}