`followSymlinks` option

[benmccann]

tinyglobby needs the option because it's an option that fast-glob offers, so libraries like netlify/build can't migrate to tinyglobby without it.

tinyglobby tries to use excludeSymlinks for this purpose today, but it doesn't work: https://github.com/SuperchupuDev/tinyglobby/issues/133

My only concern was that adding more options might slow down crawling. I did a search on GitHub and don't see anyone using excludeSymlinks except for tinyglobby and forks of it, so I think that option could be dropped if we wanted to minimize the number of available options to maximize performance.