Fix #4: Add example build script

.gitignore

@@ -1,2 +1,3 @@
 *_wrap.c
 build/
+.xmake/

readme.md

@@ -18,9 +18,27 @@
 
 ### Lua ###
 
+> Example build:
+```sh
+# This example build script requires `xmake` and `swig` installed.
+# `xmake.lua` in this repo is used to build the Lua `.so` module. Should work on Windows as well to build a `.dll`.
+# You can use Lua 5.1~5.4 too, but you need to make changes in the `xmake.lua` accordingly.
+xrepo install "luajit 2.1.0-beta3" && xmake build "swigraylib_lua"
+```
+
+> Print raylib version in the terminal:
+```sh
+# Start luajit to test. You should change path of the output library accordingly.
+luajit -i -e "package.cpath=package.cpath..';./build/linux/x86_64/release/libswig?_lua.so'"
+> raylib = require "raylib"
+> print(raylib.RAYLIB_VERSION)
+3.7
+```
+
+> Basic window in Lua:
 ```lua
+-- Original version in C: https://github.com/raysan5/raylib/blob/master/examples/core/core_basic_window.c, by Ramon Santamaria (@raysan5)
 local raylib = require "raylib"
-
 local screenWidth, screenHeight = 800, 450
 raylib.InitWindow(screenWidth, screenHeight, "raylib [core] example - basic window")
 raylib.SetTargetFPS(60)

xmake.lua

@@ -0,0 +1,38 @@
+add_rules("mode.release", "mode.debug")
+set_languages("c99")
+add_requires("raylib 3.7.0")
+
+-- Choose one of the Lua versions:
+-- add_requires("lua 5.3", {optional=true})
+-- add_requires("lua 5.4, {optional=true}")
+add_requires("luajit 2.1.0-beta3", {optional=true})
+
+target("swigraylib_lua")
+    set_kind("shared")
+    before_build(function(target)
+        local raylibDefs = {"-D_DEFAULT_SOURCE -DPLATFORM_DESKTOP -DGRAPHICS_API_OPENGL_33 -DPHYSAC_IMPLEMENTATION"}
+        if is_plat("windows") then
+            raylibDefs[#raylibDefs+1] = "-D_WIN32"
+        elseif is_plat("linux") then
+            raylibDefs[#raylibDefs+1] = "-D__linux__"
+        elseif is_plat("macosx") then
+            raylibDefs[#raylibDefs+1] = "-D__APPLE__"
+        else
+            os.raise("This xmake script doesn't support this target platform at the moment...")
+        end
+        local swigParams = {"-lua", "-no-old-metatable-bindings"}
+        for i = 1, #raylibDefs do swigParams[#swigParams+1] = raylibDefs[i] end
+        swigParams[#swigParams+1] = "raylib.i"
+        os.runv("swig", swigParams)
+        cprint("${yellow underline}SwigCmd: swig "..table.concat(swigParams, ' ').." ${clear}")
+        target:add("cxflags", raylibDefs)
+    end)
+    if is_plat("linux") then
+        add_cxflags("-fPIC")
+    end
+    add_packages("raylib")
+    add_files("raylib_wrap.c")
+
+    -- Choose one of the Lua package:
+    -- add_packages("lua")
+    add_packages("luajit")