feat: add TAP attack example with Azure OpenAI custom target

- Demonstrates Tree of Attacks with Pruning (TAP) on Azure OpenAI endpoint
- Uses CustomTarget to wrap Azure OpenAI API as attack target
- Applies character join transform for obfuscation testing
- Uses Groq Llama 4 for attacker/evaluator models
- Includes setup instructions for Azure Foundry configuration
- Early stopping at 0.75 score, max 50 trials

Author: rdheekonda