renamed some files and directories that had identical filenames. Altered some nixvim plugin options. Set up gpg signing for git commits.

modules/sys/sysenv/default.nix

@@ -0,0 +1,4 @@
+{ inputs, nixpkgs, nixvim, config, self, username, host, ... }: {
+  imports = [ (import ./sddm.nix) ] ++ [ (import ./issue.nix) ]
+    ++ [ (import ./nix.nix) ] ++ [ (import ./stylix.nix) ];
+}