add launcher

launcher/build.bat

@@ -0,0 +1,21 @@
+@echo off
+setlocal
+
+where go.exe >nul 2>&1
+if errorlevel 1 (
+    echo Go was not found in PATH.
+    exit /b 1
+)
+
+pushd "%~dp0" || exit /b 1
+go build -trimpath -ldflags "-s -w -H=windowsgui" -o start.exe start.go
+set "BUILD_EXIT=%errorlevel%"
+popd
+
+if not "%BUILD_EXIT%"=="0" (
+    echo Failed to build start.exe.
+    exit /b %BUILD_EXIT%
+)
+
+echo Built "%~dp0start.exe" successfully.
+exit /b 0