deps: update imgui to 1.92.6 and allow changing imgui font/style at run-time (#4152)

Did this while investigating #3299 which I could not reproduce.

ImGui's had a recent version that allows for dynamically scaling the
font, pretty cool, slightly improves our styling menu.

Closes #3299

third-party/imgui/imgui_stdlib.cpp

@@ -1,10 +1,22 @@
 // dear imgui: wrappers for C++ standard library (STL) types (std::string, etc.)
+
 // This is also an example of how you may wrap your own similar types.
+// TL;DR; this is using the ImGuiInputTextFlags_CallbackResize facility,
+// which also demonstrated in 'Dear ImGui Demo->Widgets->Text Input->Resize Callback'.
 
 // Changelog:
 // - v0.10: Initial version. Added InputText() / InputTextMultiline() calls with std::string
 
-// See more C++ related extension (fmt, RAII, syntaxis sugar) on Wiki:
+// Usage:
+// {
+//   #include "misc/cpp/imgui_stdlib.h"
+//   #include "misc/cpp/imgui_stdlib.cpp" // <-- If you want to include implementation without messing with your project/build.
+//   [...]
+//   std::string my_string;
+//   ImGui::InputText("my string", &my_string);
+// }
+
+// See more C++ related extension (fmt, RAII, syntactic sugar) on Wiki:
 //   https://github.com/ocornut/imgui/wiki/Useful-Extensions#cness
 
 #include "imgui.h"