change: Improve issue template for error contexts

[mathysgrapotte]

Is your change request related to a problem? Please describe.

Current issue template doesn't capture enough error details for debugging.

Describe the solution you'd like

Add "Error Context" section to bug reports requesting:

1. Stimulus version
2. Config snippet
3. Error message with context
4. Component stack

[mathysgrapotte]

example implementation for context :

from typing import Dict, List
from stimulus.exceptions import LoaderConfigError

def validate_config_structure(config: Dict, required_sections: List[str]) -> None:
    """Validate top-level config structure"""
    missing_sections = [s for s in required_sections if s not in config]
    if missing_sections:
        raise LoaderConfigError("Missing config sections").add_context(
            missing_sections=missing_sections,
            existing_sections=list(config.keys()),
            required_sections=required_sections
        )

# Usage during pipeline setup
def initialize_loader(config: dict):
    validate_config_structure(config, required_sections=["columns", "formats"])
    # Proceed with initialization