update readme with playground

README.md

@@ -9,13 +9,17 @@ This library takes a literal codepoint string and calculates the UTF-8 encoding
 ```go
 package main
 
-import "github.com/RageCage64/go-utf8-codepoint-converter/codepoint"
+import (
+	"fmt"
+
+	"github.com/RageCage64/go-utf8-codepoint-converter/codepoint"
+)
 
 func main() {
 	codepointStr := "U+1F60A"
 	utf8bytes, _ := codepoint.Convert(codepointStr)
 	fmt.Println(string(utf8bytes))
-    codepointStr := "\\U0001F603"
+	codepointStr = "\\U0001F603"
 	utf8bytes, _ = codepoint.Convert(codepointStr)
 	fmt.Println(string(utf8bytes))
 }
@@ -25,3 +29,4 @@ Result:
 😊
 😃
 ```
+Playground: https://go.dev/play/p/Nd6xxU3k7QI