feat(types): add (and fix) evaluateHandle types (#6130)

This change started as a small change to pull types from DefinitelyTyped over to
Puppeteer for the `evaluateHandle` function but instead ended up also fixing
what looks to be a long standing issue with our existing documentation.

`evaluateHandle` can in fact return an `ElementHandle` rather than a `JSHandle`.
Note that `ElementHandle` extends `JSHandle` so whilst the docs are technically
correct (all ElementHandles are JSHandles) it's confusing because JSHandles
don't have methods like `click` on them, but ElementHandles do.

if you return something that is an HTML element:

```
const button = page.evaluateHandle(() => document.querySelector('button'));
// this is an ElementHandle, not a JSHandle
```

Therefore I've updated the original docs and added a large explanation to the
TSDoc for `page.evaluateHandle`.

In TypeScript land we'll assume the function will return a `JSHandle` but you
can tell TS otherwise via the generic argument, which can only be `JSHandle`
(the default) or `ElementHandle`:

```
const button = page.evaluateHandle<ElementHandle>(() => document.querySelector('button'));
```

new-docs/puppeteer.evaluatehandlefn.md

@@ -0,0 +1,12 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [puppeteer](./puppeteer.md) &gt; [EvaluateHandleFn](./puppeteer.evaluatehandlefn.md)
+
+## EvaluateHandleFn type
+
+
+<b>Signature:</b>
+
+```typescript
+export declare type EvaluateHandleFn = string | ((...args: unknown[]) => unknown);
+```