Docs: add documentation about error handling

[leandrodamascena]

Summary

Create documentation for error handling in durable functions, explaining exception types, error response formats, and troubleshooting guidance.

Solution

Create error handlings docs with:

• Error handling overview - How errors work in durable functions
• Exception types - DurableExecutionsError, InvocationError, ValidationError, etc.
• Error response formats - AWS-compliant error response structures
• HTTP status code mappings - How errors map to HTTP status codes
• Retry strategies - Configuring retry behavior for transient failures
• Error propagation - How errors propagate through operations
• Troubleshooting guidance - Common error scenarios and solutions
• Best practices - Guidelines for effective error handling
• FAQ - Common questions about error handling
• Testing section (at the end) - How to assert on error conditions in tests with examples