feat: include README and example code in DEB package

Install README.md and example/{CMakeLists.txt,main.cpp} to
/usr/share/numpycpp/ so users can copy and build after dpkg -i.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: peng.li24

CMakeLists.txt

@@ -44,6 +44,14 @@ install(FILES
     DESTINATION lib/cmake/numpycpp
 )
 
+# ---- Docs & examples -------------------------------------------------------
+install(FILES README.md
+    DESTINATION share/numpycpp
+)
+install(DIRECTORY example/
+    DESTINATION share/numpycpp/example
+)
+
 # ---- CPack DEB packaging ----------------------------------------------------
 set(CPACK_PACKAGE_NAME                     "numpycpp-dev")
 set(CPACK_PACKAGE_VERSION                  ${PROJECT_VERSION})

example/CMakeLists.txt

@@ -0,0 +1,7 @@
+cmake_minimum_required(VERSION 3.16)
+project(numpycpp_example LANGUAGES CXX)
+
+find_package(numpycpp REQUIRED)
+
+add_executable(example main.cpp)
+target_link_libraries(example PRIVATE numpycpp::numpycpp)

example/main.cpp

@@ -0,0 +1,20 @@
+#include <numpy/core.h>
+#include <iostream>
+#include <vector>
+
+int main() {
+    double data[] = {1.0, 2.0, 3.0, 4.0, 5.0};
+
+    std::cout << "sum:  " << numpy::sum(data, 5) << std::endl;
+    std::cout << "mean: " << numpy::mean(data, 5) << std::endl;
+    std::cout << "max:  " << numpy::max(data, 5) << std::endl;
+    std::cout << "min:  " << numpy::min(data, 5) << std::endl;
+
+    double sq[5];
+    numpy::sqrt(data, sq, 5);
+    std::cout << "sqrt:";
+    for (int i = 0; i < 5; ++i) std::cout << " " << sq[i];
+    std::cout << std::endl;
+
+    return 0;
+}