docs(vendor): add version.txt tracking files for imgui, llvm, raylib, and rlImGui

vendor/rlImGui/version.txt

@@ -0,0 +1,9 @@
+Name: rlImGui
+Version: raylib 5.0 + Dear ImGui Docking integration
+Repository: https://github.com/raylib-extras/rlImGui
+Author: Jeffery Myers
+License: zlib
+Integration: Compiled via vendor/rlImGui/rlImGui.cpp (cached in build/rlImGui.obj)
+Headers:
+  - vendor/rlImGui/rlImGui.h
+  - vendor/rlImGui/rlImGuiColors.h