doc: add streaming examples (bytedance#422)

Author: liuq19

examples/example_stream_test.go

@@ -0,0 +1,37 @@
+package example
+
+import (
+	"bytes"
+	"fmt"
+	"strings"
+	"github.com/bytedance/sonic"
+)
+
+// This example uses a Decoder to decode a stream of distinct JSON values.
+func ExampleStreamDecoder() {
+	var o =  map[string]interface{}{}
+	var r = strings.NewReader(`{"a":"b"}{"1":"2"}`)
+	var dec = sonic.ConfigDefault.NewDecoder(r)
+	dec.Decode(&o)
+	dec.Decode(&o)
+	fmt.Printf("%+v", o)
+	// Output:
+	// map[1:2 a:b]
+}
+
+
+// This example uses a Encoder to encode streamingly.
+func ExampleStreamEncoder() {
+	var o1 = map[string]interface{}{
+		"a": "b",
+	}
+	var o2 = 1
+	var w = bytes.NewBuffer(nil)
+	var enc = sonic.ConfigDefault.NewEncoder(w)
+	enc.Encode(o1)
+	enc.Encode(o2)
+	fmt.Println(w.String())
+	// Output:
+	// {"a":"b"}
+	// 1
+}