RStudio has become Posit about guide

[maltelueken]

I didn't find any broken links yet, but I will do a sweep to update the links which are now forwarded to posit.co. The IDE is still called RStudio so I don't think we need to rename anything since we are referencing the IDE and not the company behind it.

[egpbos]

To clarify: the link I mention indeed doesn't seem to be broken for normal users using normal browsers, but the link checker GitHub Action does report it broken. My guess is that posit maybe blocks requests from GH Action servers or perhaps that Lychee (the link checker) doesn't know how to redirect, like normal browsers do. Either way, the rstudio.com links all redirect to posit.co, so probably just a find-and-replace on that would make sense anyway :)

Thanks for picking this up!

By the way, I think it would also make a lot of sense if you put your name at the top of the chapter as its maintainer!