Create a search function for the resources

[cafelow]

This is something a few people have asked me for so I'd like it prioritised.

I'm hoping there is an easy way of doing this so we can get a quick and dirty solution sorted.
E.g. put a google search bar into the header, or into a separate page which can be a category under "Contribute or Contact Us".

I know the initial plan was to have a "search all EA websites". If it is no harder to do we could have a radio button for "search EA Hub resources" or "search 10 EA websites".
But the ability to search the resources is the priority.

BTW: Post on this is one of many requests for this! https://forum.effectivealtruism.org/posts/BMdsMbrho78Jmfawj/how-to-find-ea-documents-on-a-particular-topic

[sebgrebe]

duplicate of #1104