Escape quotes and new lines in JSON strings

Inside JSON strings, special characters must be escaped with backslashes.

{
  "message": "She said: "hello"",
  "path": "C:\temp\file.txt",
  "multiline": "line one
line two"
}

• \" for double quote
• \\ for backslash
• \n for newline
• \t for tab

If possible, avoid manual string building — use language JSON serializers to escape automatically.