add text encoding params to STDIO client - #120

This PR adds text encoding parameters to the STDIO Client. This allows the SDK user to configure how the text encoder will respond to errors and set the encoding used.

Motivation and Context

Fixes #110

This fixes an issue I was encountering in some of my programs when handling text from the internet.

How Has This Been Tested?

All of the included unit tests are passing with this (via uv run pytest)
Styling was checked via ruff check
I modified the example reproduction in #110 with an implementation of the new features (https://github.com/SecretiveShell/MCP-SDK-JSON-DECODE-ERROR/tree/test-fix)

Breaking Changes

None, all default values remain the same.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

This was discussed in discord, and it was suggested that it would be beneficial to add extra test cases for this specific error. Currently this PR does not include this