Episode 3: Arrays

Arrays + Memory layout - contig. mem. access
a. neat (perhaps optional) Fortran feature: we can choose the lower bound, too!
b. Array slices, expressions and masks (in a hint mention where and trouble with openmp)

See the full curriculum in context at the Discussion:
https://github.com/carpentries-incubator/intro-to-modern-fortran/discussions/6