Support to parse a file with file path.

[ikorin24]

Add APIs

• in U8Xml.XmlParser class

  • static XmlObject XmlParser.ParseFile(string filePath)
  • static XmlObject XmlParser.ParseFile(string filePath, Encoding encoding)

• in U8Xml.Unsafes.XmlParserUnsafe class

  • static XmlObjectUnsafe XmlParser.ParseFileUnsafe(string filePath)
  • static XmlObjectUnsafe XmlParser.ParseFileUnsafe(string filePath, Encoding encoding)