Add a "suggested readings for functional programming" wiki page

[smiths]

As pointed out by @cd155 in #2967, we do not have much information in our repo on how to get started with functional programming. A wiki page with suggested readings could help new project members get up to speed.

[balacij]

A small note for the future, LearnYouAHaskell's website has been down for a while, but, luckily, there's a community version (with approval from the original author of LYAH) with source available too.

[smiths]

Thank you @balacij for posting the link. I noticed recently that the original LearnYouAHaskell website was gone. I often recommend this resource, so I was disappointed to not be able to find it. I actually spent some unsuccessful google time trying to find it. Thank you for sending the link. We definitely should include this in our list of functional programming resources.