feat: add experimental io interface

[peter-jerry-ye]

No description provided.

[peter-jerry-ye-code-review]

README.md lacks meaningful content

Category
Maintainability
Code Snippet

username/hello

Recommendation
Add proper documentation including: module purpose, installation instructions, usage examples, and API reference
Reasoning
A good README is essential for module adoption and maintenance. Current placeholder content provides no value to users.

Missing documentation for IO functions

Category
Maintainability
Code Snippet
fn print(@string.View) -> Unit
fn println(@string.View) -> Unit
Recommendation
Add documentation comments explaining each function's purpose, parameters, and error conditions
Reasoning
Public API functions should be well-documented to help users understand their behavior, especially for error-producing functions like read_line()

Unclear error handling semantics

Category
Correctness
Code Snippet
fn is_eof(Error) -> Bool
Recommendation
Consider adding error type definitions and document possible error conditions for read_char() and read_line()
Reasoning
The relationship between the fallible operations (marked with !) and is_eof() needs to be clearly specified for proper error handling