docs(anthropic_completion.md): add doc on anthropic /v1/messages endpoint support

docs/my-website/docs/anthropic_completion.md

@@ -0,0 +1,54 @@
+# [BETA] Anthropic `/v1/messages`
+
+Call 100+ LLMs in the Anthropic format. 
+
+
+1. Setup config.yaml 
+
+```yaml
+model_list:
+  - model_name: my-test-model
+    litellm_params:
+      model: gpt-3.5-turbo
+```
+
+2. Start proxy 
+
+```bash
+litellm --config /path/to/config.yaml
+```
+
+3. Test it! 
+
+```bash
+curl -X POST 'http://0.0.0.0:4000/v1/messages' \
+-H 'x-api-key: sk-1234' \
+-H 'content-type: application/json' \
+-D '{
+    "model": "my-test-model",
+    "max_tokens": 1024,
+    "messages": [
+        {"role": "user", "content": "Hello, world"}
+    ]
+}'
+```
+
+## Test with Anthropic SDK 
+
+```python
+import os
+from anthropic import Anthropic
+
+client = Anthropic(api_key="sk-1234", base_url="http://0.0.0.0:4000") # 👈 CONNECT TO PROXY
+
+message = client.messages.create(
+    messages=[
+        {
+            "role": "user",
+            "content": "Hello, Claude",
+        }
+    ],
+    model="my-test-model", # 👈 set 'model_name'
+)
+print(message.content)
+```

docs/my-website/sidebars.js

@@ -117,6 +117,7 @@ const sidebars = {
         "text_to_speech",
         "assistants",
         "batches",
+        "anthropic_completion"
       ],
     },
     {