readme: add initial readme

Author: a1batross

README.md

@@ -0,0 +1,28 @@
+# mainui_cpp
+
+Main Menu UI for Xash3D FWGS engine, built entirely in C++.
+
+Key features:
+* Custom font renderer with multiple backends based on FreeType, stb_truetype and GDI on Windows
+* Unicode and l10n support
+* Completely self-contained, just clone this repo (with --recursive) and add to your mod
+* Complex widget containers system, ability to put widget into containers into container
+* Window system as a continuation of containers system
+* Client-side menus (needs to be documented)
+
+### Including mainui_cpp in your mod
+
+1. Clone this repo: `git clone --recursive https://github.com/FWGS/mainui_cpp` to your mod source code tree.
+2. If you use:
+* CMake: invoke `add_subdirectory(mainui_cpp)` in your CMakeLists.txt file
+* Waf/WAiFu: invoke `ctx.add_subdirectory('mainui_cpp')` in your wscript file
+* Visual Studio: if you want to build it from your mod tree, include `vs2022/mainui_cpp.vcxproj` to your mod solution, or use `vs2022/mainui_cpp.sln`.
+3. Place your built `menu.dll`/`libmenu.so` ALONGSIDE your `client.dll`/`client.so`.
+4. Check that everything is working and happy hacking!
+
+If you have any troubles setting this up, create an issue in https://github.com/FWGS/mainui_cpp/issues.
+
+### Notes and restrictions
+
+* mainui_cpp doesn't supports original Xash3D anymore. If it's possible, you can switch to Xash3D FWGS, otherwise you're on your own. I will accept patches to enable other Xash3D forks, but I won't support them on my own.
+