feat: known endpoint, xAI (#161)

pages/docs/configuration/librechat_yaml/ai_endpoints/xai.mdx

@@ -0,0 +1,30 @@
+---
+title: xAI
+description: Example configuration for xAI
+---
+
+# [xAI](https://console.x.ai/)
+
+> xAI API key: [x.ai](https://console.x.ai/)
+
+**Notes:**
+
+- **Known:** icon provided.
+
+```yaml filename="librechat.yaml"
+    - name: "xai"
+      apiKey: "${XAI_API_KEY}"
+      baseURL: "https://api.x.ai/v1"
+      models:
+        default: ["grok-beta"]
+        fetch: false
+      titleConvo: true
+      titleMethod: "completion"
+      titleModel: "grok-beta"
+      summarize: false
+      summaryModel: "grok-beta"
+      forcePrompt: false
+      modelDisplayLabel: "Grok"
+```
+
+![image](https://github.com/user-attachments/assets/815173c4-489f-4944-b7bf-5602e4a6e8e8)

pages/docs/configuration/librechat_yaml/object_structure/custom_endpoint.mdx

@@ -112,13 +112,14 @@ iconURL: https://github.com/danny-avila/LibreChat/raw/main/docs/assets/LibreChat
 * There are also "known endpoints" (case-insensitive), which have icons provided. If your endpoint `name` matches the following names, you should omit this field:
   - "Mistral"
   - "OpenRouter"
-  - "Groq"
+  - "groq"
   - "APIpie"
   - "Anyscale"
   - "Fireworks"
   - "Perplexity"
   - "together.ai"
-  - "Ollama"
+  - "ollama"
+  - "xai"
   - "MLX"
 
 ## models