feat(integration): add promptfoo LLM testing framework

Add promptfoo to the awesome-deepseek-integration library with:
- English and Chinese documentation
- Basic setup and usage guides
- Example configuration for DeepSeek model testing
- Integration entry in both README.md and README_cn.md

docs/promptfoo/README.md

@@ -0,0 +1,70 @@
+# promptfoo
+
+[promptfoo](https://promptfoo.dev) is an open-source framework for testing and evaluating LLM outputs. It helps you compare DeepSeek models with other LLMs (like o1, GPT-4o, Claude 3.5, Llama3.3, and Gemini) and test LLMs and LLM applications for security vulnerabilities. You can:
+
+- Run side-by-side comparisons between models
+- Check output quality and consistency
+- Generate test reports
+
+## Setup
+
+1. Install promptfoo:
+
+```bash
+npm install -g promptfoo
+# or
+brew install promptfoo
+```
+
+2. Configure API keys:
+
+```bash
+export DEEPSEEK_API_KEY=your_api_key
+# Add other API keys as needed
+```
+
+## Quick Start
+
+Create a configuration file `promptfooconfig.yaml`:
+
+```yaml
+providers:
+  - deepseek:deepseek-reasoner # DeepSeek-R1
+  - openai:o1
+
+prompts:
+  - 'Solve this step by step: {{math_problem}}'
+
+tests:
+  - vars:
+      math_problem: 'What is the derivative of x^3 + 2x with respect to x?'
+    assert:
+      - type: contains
+        value: '3x^2' # Check for correct answer
+      - type: llm-rubric
+        value: 'Response shows clear steps'
+      - type: cost
+        threshold: 0.05 # Maximum cost per request
+```
+
+Run tests:
+
+```bash
+promptfoo eval
+```
+
+View results in your browser:
+
+```bash
+promptfoo view
+```
+
+## Example Project
+
+Check out our [example](https://github.com/promptfoo/promptfoo/tree/main/examples/deepseek-r1-vs-openai-o1) that compares r1 and o1 on MMLU.
+
+## Resources
+
+- [Documentation](https://promptfoo.dev/docs/providers/deepseek)
+- [GitHub Repository](https://github.com/promptfoo/promptfoo)
+- [Community Discord](https://discord.gg/promptfoo)