docs: add gpt-4 as llm FAQ (#731)

docs/get-start/faq.mdx

@@ -0,0 +1,16 @@
+---
+title: ❓ Frequently Asked Questions
+description: 'Collections of all the frequently asked questions about Embedchain'
+---
+
+## How to use GPT-4 as the LLM model
+
+```python
+
+from embedchain import App
+from embedchain.config import LlmConfig
+
+app = App()
+app.add("https://en.wikipedia.org/wiki/Elon_Musk")
+app.query("How many companies does Elon Musk run and name those?", config=LlmConfig(model="gpt-4))
+```

docs/mint.json

@@ -32,7 +32,7 @@
   "navigation": [
     {
       "group": "Get started",
-      "pages": ["get-start/quickstart", "get-start/introduction"]
+      "pages": ["get-start/quickstart", "get-start/introduction", "get-start/faq"]
     },
     {
       "group": "Advanced",