docs: add basic example for cpp binding (apache#3108)

* chore: add basic example for cpp binding

Signed-off-by: silver-ymz <yinmingzhuo@gmail.com>

* typo

Signed-off-by: silver-ymz <yinmingzhuo@gmail.com>

* typo

Signed-off-by: silver-ymz <yinmingzhuo@gmail.com>

* use exist commit

Signed-off-by: silver-ymz <yinmingzhuo@gmail.com>

---------

Signed-off-by: silver-ymz <yinmingzhuo@gmail.com>

examples/README.md

@@ -7,3 +7,4 @@ The goal of these documents is to provide you with everything you need to start
 ## Examples
 
 - [Rust](rust/README.md)
+- [C++](cpp/README.md)

examples/cpp/CMakeLists.txt

@@ -0,0 +1,21 @@
+cmake_minimum_required(VERSION 3.10)
+project(opendal-cpp-examples)
+
+set(CMAKE_CXX_STANDARD 17)
+
+include(FetchContent)
+FetchContent_Declare(
+  opendal-cpp
+  GIT_REPOSITORY https://github.com/apache/incubator-opendal.git
+  GIT_TAG        4b02228f7fe9a7c0f21a1660fee95716910c7a0a
+  SOURCE_SUBDIR  bindings/cpp
+)
+FetchContent_MakeAvailable(opendal-cpp)
+
+add_executable(basic-example basic.cpp)
+target_link_libraries(basic-example opendal_cpp)
+include_directories(basic-example opendal_cpp)
+
+if(APPLE)
+    target_link_libraries(basic-example "-framework CoreFoundation -framework Security")
+endif()

examples/cpp/README.md

@@ -0,0 +1,13 @@
+# OpenDAL Cpp Examples
+
+Thank you for using OpenDAL Cpp Core!
+
+## Run Examples
+
+```bash
+mkdir build
+cd build
+cmake ..
+make
+./basic-example
+```

examples/cpp/basic.cpp

@@ -0,0 +1,25 @@
+#include "opendal.hpp"
+
+#include <string>
+#include <vector>
+#include <iostream>
+
+int main() {
+  char s[] = "memory";
+  std::vector<uint8_t> data = {'a', 'b', 'c'};
+
+  // Init operator
+  opendal::Operator op = opendal::Operator(s);
+
+  // Write data to operator
+  op.write("test", data);
+
+  // Read data from operator
+  auto res = op.read("test"); // res == data
+
+  // Using reader
+  auto reader = op.reader("test");
+  opendal::ReaderStream stream(reader);
+  std::string res2;
+  stream >> res2; // res2 == "abc"
+}