etc: support experimental official Nix installer

doc/known-files/4e8f7cb9b699511f4ba5f9d5f8de1c9f5efb5c607de88faf5f58b8b9cb38edbf

@@ -0,0 +1,7 @@
+
+# Set up Nix only on SSH connections
+# See: https://github.com/DeterminateSystems/nix-installer/pull/714
+if [ -e '/nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh' ] && [ -n "${SSH_CONNECTION:-}" ] && [ "${SHLVL:-0}" -eq 1 ]; then
+    . '/nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh'
+fi
+# End Nix

doc/known-files/71f7fdc9f6c9e55ca0f2e6f85137037d660b3224a34d59305e8530ca292bc734

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+# Written by https://github.com/NixOS/nix-installer
+# The contents below are based on options specified at installation time.
+

doc/known-files/74ee0ae5ad21a1b101617685fd3d001f74a9466d9d763d92eb75b99cc740db91

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+# Generated by https://github.com/NixOS/nix-installer
+# See `/nix/nix-installer --version` for the version details.
+
+extra-experimental-features = nix-command flakes
+always-allow-substitutes = true
+bash-prompt-prefix = (nix:$name)\040
+max-jobs = auto
+extra-nix-path = nixpkgs=flake:nixpkgs
+
+!include nix.custom.conf