In the heirarchy, both "Terraform Language" and "Functions" are "up" from
the individual function reference pages, so we'll class them as such to
use the back-facing arrow instead of the forward-facing arrow.
Previously we just listed out all of the functions in alphabetical order
inside the "Interpolation Syntax" page, but that format doesn't leave much
room for details and usage examples.
Now we give each function its own page, and categorize them for easier
navigation. While many functions are very simple and don't really warrant
a full page, certain functions do have additional details that are worth
mentioning and this structure scales better for those more complicated
functions.
So far this includes only the numeric and string functions. Other
categories will follow in subsequent commits.
Martin Atkins