doc: Add Antigravity to MCP client list in README (#1419)

README.md

@@ -72,6 +72,26 @@ amp mcp add playwright -- npx @playwright/mcp@latest
 
 </details>
 
+<details>
+<summary>Antigravity</summary>
+
+Add via the Antigravity settings or by updating your configuration file:
+
+```json
+{
+  "mcpServers": {
+    "playwright": {
+      "command": "npx",
+      "args": [
+        "@playwright/mcp@latest"
+      ]
+    }
+  }
+}
+```
+
+</details>
+
 <details>
 <summary>Claude Code</summary>