Getting Started page

[jducoeur]

We need at least an introductory page ASAP, or possibly two since there are two major topics:

• How to get started using TL (pointers to the libraries, list the central ones, pointers to useful books and webpages to understand FP)
• How to get started contributing to TL (pointers to the Discord, the "good first issues" list, etc)

It's not obvious where these go on the website -- let's try not to bikeshed that too much, but it's the camel's nose in the tent of thinking about the information architecture of the site.