different codebases use different formatters. autofmt looks for project
configuration to pick the correct formatter, allowing an editor to
simply point to the script and have all ambiguities resolved.
this commit overhauls the conform configuration to set up autofmt
correctly, as well installing it with 'pkgs.autofmt'
closes#6
previously mkDefault/mkOverride on vim.options would go before nvf's
defaults, which would basically make none of them apply. now it doesn't
use an override priority, at the cost that overriding any of these in a
user config will not work without mkForce.
also enable swapfiles, closes#1
