docs(perplexity.md): show how to get 'return_citations'

docs/my-website/docs/providers/perplexity.md

@@ -1,3 +1,6 @@
+import Tabs from '@theme/Tabs';
+import TabItem from '@theme/TabItem';
+
 # Perplexity AI (pplx-api)
 https://www.perplexity.ai
 
@@ -38,7 +41,7 @@ for chunk in response:
 
 
 ## Supported Models
-All models listed here https://docs.perplexity.ai/docs/model-cards are supported
+All models listed here https://docs.perplexity.ai/docs/model-cards are supported.  Just do `model=perplexity/<model-name>`.
 
 | Model Name               | Function Call                                                                                                                                                      |
 |--------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------|
@@ -60,3 +63,72 @@ All models listed here https://docs.perplexity.ai/docs/model-cards are supported
 
 
 
+
+## Return citations 
+
+Perplexity supports returning citations via `return_citations=True`. [Perplexity Docs](https://docs.perplexity.ai/reference/post_chat_completions). Note: Perplexity has this feature in **closed beta**, so you need them to grant you access to get citations from their API. 
+
+If perplexity returns citations, LiteLLM will pass it straight through. 
+
+:::info
+
+For passing more provider-specific, [go here](../completion/provider_specific_params.md)
+:::
+
+<Tabs>
+<TabItem value="sdk" label="SDK">
+
+```python
+from litellm import completion
+import os
+
+os.environ['PERPLEXITYAI_API_KEY'] = ""
+response = completion(
+    model="perplexity/mistral-7b-instruct", 
+    messages=messages,
+    return_citations=True
+)
+print(response)
+```
+
+</TabItem>
+<TabItem value="proxy" label="PROXY">
+
+1. Add perplexity to config.yaml
+
+```yaml
+model_list:
+  - model_name: "perplexity-model"
+    litellm_params:
+      model: "llama-3.1-sonar-small-128k-online"
+      api_key: os.environ/PERPLEXITY_API_KEY
+```
+
+2. Start proxy 
+
+```bash
+litellm --config /path/to/config.yaml
+```
+
+3. Test it! 
+
+```bash
+curl -L -X POST 'http://0.0.0.0:4000/chat/completions' \
+-H 'Content-Type: application/json' \
+-H 'Authorization: Bearer sk-1234' \
+-d '{
+    "model": "perplexity-model",
+    "messages": [
+      {
+        "role": "user",
+        "content": "Who won the world cup in 2022?"
+      }
+    ],
+    "return_citations": true
+}'
+```
+
+[**Call w/ OpenAI SDK, Langchain, Instructor, etc.**](../proxy/user_keys.md#chatcompletions)
+
+</TabItem>
+</Tabs>