partners: Add Perplexity Chat Integration (#30618)

Perplexity's importance in the space has been growing, so we think it's
time to add an official integration!

Note: following the release of `langchain-perplexity` to `pypi`, we
should be able to add `perplexity` as an extra in
`libs/langchain/pyproject.toml`, but we're blocked by a circular import
for now.

---------

Co-authored-by: Eugene Yurtsev <eyurtsev@gmail.com>
Co-authored-by: Chester Curme <chester.curme@gmail.com>

docs/src/theme/ChatModelTabs.js

@@ -218,6 +218,13 @@ ${llmVarName} = ChatWatsonx(
       apiKeyName: "XAI_API_KEY",
       packageName: "langchain-xai",
     },
+    {
+      value: "perplexity",
+      label: "Perplexity",
+      model: "llama-3.1-sonar-small-128k-online",
+      apiKeyName: "PPLX_API_KEY",
+      packageName: "langchain-perplexity",
+    }
   ].map((item) => ({
     ...item,
     ...overrideParams?.[item.value],

docs/src/theme/FeatureTables.js

@@ -237,6 +237,17 @@ const FEATURE_TABLES = {
                 "local": false,
                 "apiLink": "https://python.langchain.com/api_reference/xai/chat_models/langchain_xai.chat_models.ChatXAI.html"
             },
+            {
+                "name": "ChatPerplexity",
+                "package": "langchain-perplexity",
+                "link": "perplexity",
+                "structured_output": true,
+                "tool_calling": false,
+                "json_mode": true,
+                "multimodal": true,
+                "local": false,
+                "apiLink": "https://python.langchain.com/api_reference/perplexity/chat_models/langchain_perplexity.chat_models.ChatPerplexity.html"
+            }
         ],
     },
     llms: {