We would much rather have that file in assets/ but it seems this
wasn't being picked up by lektor, so this will have to do for
now.
This is also how the Jenkins build script was doing it:
https://gitweb.torproject.org/project/jenkins/tools.git/tree/slaves/linux/lektor-website/build#n101
Ideally, we wouldn't have an .htaccess at all since those have significant performance impact on the webserver, but we just want to restore service to complete the %Retire Jenkins milestone.