feat(ai-proxy): add OpenRouter provider support (#2823)

plugins/wasm-go/extensions/ai-proxy/README_EN.md

@@ -144,6 +144,10 @@ For Groq, the corresponding `type` is `groq`. It has no unique configuration fie
 
 For Grok, the corresponding `type` is `grok`. It has no unique configuration fields.
 
+#### OpenRouter
+
+For OpenRouter, the corresponding `type` is `openrouter`. It has no unique configuration fields.
+
 #### ERNIE Bot
 
 For ERNIE Bot, the corresponding `type` is `baidu`. It has no unique configuration fields.
@@ -894,6 +898,63 @@ provider:
 }
 ```
 
+### Using OpenAI Protocol Proxy for OpenRouter Service
+
+**Configuration Information**
+
+```yaml
+provider:
+  type: openrouter
+  apiTokens:
+    - 'YOUR_OPENROUTER_API_TOKEN'
+  modelMapping:
+    'gpt-4': 'openai/gpt-4-turbo-preview'
+    'gpt-3.5-turbo': 'openai/gpt-3.5-turbo'
+    'claude-3': 'anthropic/claude-3-opus'
+    '*': 'openai/gpt-3.5-turbo'
+```
+
+**Example Request**
+
+```json
+{
+  "model": "gpt-4",
+  "messages": [
+    {
+      "role": "user",
+      "content": "Hello, who are you?"
+    }
+  ],
+  "temperature": 0.7
+}
+```
+
+**Example Response**
+
+```json
+{
+  "id": "gen-1234567890abcdef",
+  "object": "chat.completion",
+  "created": 1699123456,
+  "model": "openai/gpt-4-turbo-preview",
+  "choices": [
+    {
+      "index": 0,
+      "message": {
+        "role": "assistant",
+        "content": "Hello! I am an AI assistant powered by OpenRouter. I can help answer questions, assist with creative tasks, engage in conversations, and more. How can I assist you today?"
+      },
+      "finish_reason": "stop"
+    }
+  ],
+  "usage": {
+    "prompt_tokens": 12,
+    "completion_tokens": 35,
+    "total_tokens": 47
+  }
+}
+```
+
 ### Using Auto Protocol Compatibility
 
 The plugin now supports automatic protocol detection, capable of handling both OpenAI and Claude protocol format requests simultaneously.