feat: add documentation (#8593)

docs/api/puppeteer.browsercontext.isincognito.md

@@ -0,0 +1,23 @@
+---
+sidebar_label: BrowserContext.isIncognito
+---
+
+# BrowserContext.isIncognito() method
+
+Returns whether BrowserContext is incognito. The default browser context is the only non-incognito browser context.
+
+**Signature:**
+
+```typescript
+class BrowserContext {
+  isIncognito(): boolean;
+}
+```
+
+**Returns:**
+
+boolean
+
+## Remarks
+
+The default browser context cannot be closed.