add path based redirects

up to now, those were managed outside of this repo, which as
unsurprisingly a real hassle to deal with if one wanted to prevent URLs
from breaking when moving pages around. this change removes a large part
of the friction involved in moving content in the Nix manual.

possible next steps for further automation:
- check for content that moved and warn if it's not reachable from
  links that were valid prior to a change
- create redirect rules automatically based on this information

(cherry picked from commit 2b7016cc56d12e67de9f1f25b18311866a26a5fe)

0 files changed, 0 insertions, 0 deletions