Add new example code

Author: zhengchun

README.md

@@ -190,24 +190,49 @@ expr, err := xpath.Compile("count(//book)")
 price := expr.Evaluate(xmlquery.CreateXPathNavigator(doc)).(float64)
 ```
 
-FAQ
+Advanced Features
 ====
 
-#### `Find()` vs `QueryAll()`, which is better?
-
-`Find` and `QueryAll` both do the same thing: searches all of matched XML nodes.
-`Find` panics if provided with an invalid XPath query, while `QueryAll` returns
-an error.
+### Parse `UTF-16` XML file with `ParseWithOptions()`.
 
-#### Can I save my query expression object for the next query?
+```go
+f, _ := os.Open(`UTF-16.XML`)
+// Convert UTF-16 XML to UTF-8
+utf16ToUtf8Transformer := unicode.UTF16(unicode.LittleEndian, unicode.IgnoreBOM).NewDecoder()
+utf8Reader := transform.NewReader(f, utf16ToUtf8Transformer)
+// Sets `CharsetReader`
+options := xmlquery.ParserOptions{
+	Decoder: &xmlquery.DecoderOptions{
+		CharsetReader: func(charset string, input io.Reader) (io.Reader, error) {
+			return input, nil
+		},
+	},
+}
+doc, err := xmlquery.ParseWithOptions(utf8Reader, options)
+```
 
-Yes, you can. We provide `QuerySelector` and `QuerySelectorAll` methods; they 
-accept your query expression object.
+### Query with custom namespace prefix.
 
-Caching a query expression object avoids recompiling the XPath query 
-expression, improving query performance.
+```go
+s := `<?xml version="1.0" encoding="UTF-8"?>
+<pd:ProcessDefinition xmlns:pd="http://xmlns.xyz.com/process/2003" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
+<pd:activity name="Invoke Request-Response Service">
+<pd:type>RequestReplyActivity</pd:type>
+<pd:resourceType>OpClientReqActivity</pd:resourceType>
+<pd:x>300</pd:x>
+<pd:y>80</pd:y>
+</pd:activity>
+</pd:ProcessDefinition>`
+nsMap := map[string]string{
+	"q": "http://xmlns.xyz.com/process/2003",
+	"r": "http://www.w3.org/1999/XSL/Transform",
+	"s": "http://www.w3.org/2001/XMLSchema",
+}
+expr, _ := xpath.CompileWithNS("//q:activity", nsMap)
+node := xmlquery.QuerySelector(doc, expr)
+```
 
-#### Create XML document.
+#### Create XML document without call `xml.Marshal`.
 
 ```go
 doc := &xmlquery.Node{
@@ -237,13 +262,34 @@ title_text := &xmlquery.Node{
 }
 title.FirstChild = title_text
 channel.FirstChild = title
-fmt.Println(doc.OutputXML(true))
-// <?xml version="1.0"?><rss><channel><title>W3Schools Home Page</title></channel></rss>
 
+fmt.Println(doc.OutputXML(true))
 fmt.Println(doc.OutputXMLWithOptions(WithOutputSelf()))
-// <?xml version="1.0"?><rss><channel><title>W3Schools Home Page</title></channel></rss>
 ```
 
+Output:
+
+```xml
+<?xml version="1.0"?><rss><channel><title>W3Schools Home Page</title></channel></rss>
+```
+
+FAQ
+====
+
+#### `Find()` vs `QueryAll()`, which is better?
+
+`Find` and `QueryAll` both do the same thing: searches all of matched XML nodes.
+`Find` panics if provided with an invalid XPath query, while `QueryAll` returns
+an error.
+
+#### Can I save my query expression object for the next query?
+
+Yes, you can. We provide `QuerySelector` and `QuerySelectorAll` methods; they 
+accept your query expression object.
+
+Caching a query expression object avoids recompiling the XPath query 
+expression, improving query performance.
+
 Questions
 ===
 Please let me know if you have any questions