Add HTTP 302 redirection via .htaccess

[k3rs3d]

(Idea from Eamon - @eamon@social.coop - https://git.eamoncaddigan.net/)

We can generate/modify a .htaccess file to make a web server redirect pages instead of making the visitor's browser do the redirecting. This would be more efficient but would require the webring admin to have control over the web server (ie probably self-hosted, not hosted on a service like Neocities or GH Pages).
So for example the server itself would redirect visitors to example.com/slug/next/ to the proper site in the ring's sequence. Visitors would never load a page from example.com/slug/next (which is how ringfairy currently works)
So, ringfairy should have a config option to enable/disable generating/modifying a .htaccess file. By default this should be disabled.