Change Docs to not reference unmaintained library

[D-Pagey]

Hello,

I have recently been trying to build a multi-select component in a form with useFetcher. I tried to stick to the docs as close as possible, which reference Reach UI's Combobox, and I struggled to get the solution working. I then found that the library isn't maintained anymore - Reach UI is not currently maintained

Would it be ok to change these Remix docs: useFetcher - examples and API Routes to use a currently maintained library such as Downshift?

I'm happy to create the PR to change the docs with a Downshift example, but wanted to check first.