Update docs for provider changes

[JCaraballo113]

So it seems like the library property from useEthers was changed and now you get a typescript error that library.provider no longer exists. But I can confirm it's still there since I am using it to trigger network changes on user's metamask wallet. My question is what is the proper way of doing library.provider.request now

[JCaraballo113]

I found how you do this now but just by fiddling around and not the docs. This is how you would add a new ethereum chain to their metamask for example

await library.send('wallet_addEthereumChain', [
  params,
]);