Document existing IO functionalities

[kings177]

Bend currently has implemented basic IO operations for Open, Close, Read and Write. This task involves creating a comprehensive documentation for these existing functions.

1. What to document:

1. Function definition
2. Brief description
3. Parameters
4. Return value
5. Possible errors
6. Examples
7. Notes or additional information

2. Template to folow:

Brief description of what the function does.

Parameters:

• param1: description of param1
• param2: description of param2

Returns:

• description of return value

Raises:

• ErrorType1: description of when this error occurs
• ErrorType2: description of when this error occurs

Examples:

# Example usage
result = function_name(arg1, arg2)

Notes:

Any additional information or considerations.

Reference materials:

IO Functions Rust's file system Elixir's file system