This commit isn't cherry-picked from upstream. Instead, the
.editorconfig file was copied as-is from the upstream PR. Then,
`eclint -fix .` was ran to make everything conform to editorconfig. This
should be identical in impact, but it saves a lot of headache from
resolving useless merge conflicts.
Upstream-PR: https://github.com/DeterminateSystems/nix-installer/pull/1182
Change-Id: I22f03d18b3d685ff16b08bf8df0720e0f796d501
KFears
