doc: update readme and example

Author: SSARCandy

README.md

@@ -9,34 +9,39 @@ Yet another `.ini` parser for modern c++ (made for cpp17), inspired and extend f
 
 ## Example
 
+The `config.ini`'s content is something looks like:
+
+```
+[section1]
+any=5
+
+[section2]
+any_vec = 1 2 3
+```
+
 ```cpp
-#include "ini/INIReader.h"
+#include "ini/ini.h"
 
 int main() {
     inih::INIReader r{"./test/fixtures/config.ini"};
 
+    // Get and parse the ini value
     const auto& v1 = r.Get<std::string>("section1", "any"); // "5"
     const auto& v2 = r.Get<int>("section1", "any"); // 5
     const auto& v3 = r.Get<double>("section1", "any"); // 5.0
     const auto& v4 = r.GetVector<float>("section2", "any_vec"); // [1.0, 2.0, 3.0]
     const auto& v5 = r.GetVector<std::string>("section2", "any_vec"); // ["1", "2", "3"]
 
+    // And also support writing to new ini file.
+    r.InsertEntry("new_section", "key1", 5); // section and key not exist
+    inih::INIWriter::write("output.ini", r); // Dump ini to file
+
     return 0;
 }
 ```
 
-The `config.ini`'s content is something looks like:
-
-```
-[section1]
-any=5
-
-[section2]
-any_vec = 1 2 3
-```
-
 To learn more, please refer to [test folder](https://github.com/SSARCandy/ini-cpp/tree/master/test), it covered ALL utilities.
 
 ## Install
 
-Simply copy the header file `ini/INIReader.h` to your project, then done. 
+Simply copy the header file `ini/ini.h` to your project, then done. 

example.cpp

@@ -3,7 +3,7 @@
 #include <typeinfo>
 #include <boost/core/demangle.hpp>
 
-#include "ini/INIReader.h"
+#include "ini/ini.h"
 using namespace inih;
 
 namespace bc = boost::core;
@@ -31,5 +31,14 @@ int main() {
     std::cout << "v4 = "; for (auto& v : v4) std::cout << v << " "; std::cout << ", which is type: " << bc::demangle(typeid(v4).name()) << std::endl;
     std::cout << "v5 = "; for (auto& v : v5) std::cout << v << " "; std::cout << ", which is type: " << bc::demangle(typeid(v5).name()) << std::endl;
 
+    // section exist, key not exist
+    r.InsertEntry("section1", "my_custom_key", "hello world");
+
+    // section&key not exist
+    r.InsertEntry("new_section", "key1", 5);
+
+    // Dump ini to file
+    INIWriter::write("output.ini", r);
+
     return 0;
 }