feat: add documentation (#8593)

docs/api/puppeteer.page._.md

@@ -0,0 +1,27 @@
+---
+sidebar_label: Page.$
+---
+
+# Page.$() method
+
+Runs `document.querySelector` within the page. If no element matches the selector, the return value resolves to `null`.
+
+**Signature:**
+
+```typescript
+class Page {
+  $<Selector extends keyof HTMLElementTagNameMap>(
+    selector: Selector
+  ): Promise<ElementHandle<HTMLElementTagNameMap[Selector]> | null>;
+}
+```
+
+## Parameters
+
+| Parameter | Type     | Description                                                                                                                             |
+| --------- | -------- | --------------------------------------------------------------------------------------------------------------------------------------- |
+| selector  | Selector | A <code>selector</code> to query page for [selector](https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Selectors) to query page for. |
+
+**Returns:**
+
+Promise&lt;[ElementHandle](./puppeteer.elementhandle.md)&lt;HTMLElementTagNameMap\[Selector\]&gt; \| null&gt;