feat(nixos): migrate system configuration

configs/nixos/modules/shell/fish/functions/copy.fish

@@ -0,0 +1,8 @@
+set count (count $argv | tr -d \n)
+if test "$count" = 2; and test -d "$argv[1]"
+    set from (echo $argv[1] | trim-right /)
+    set to (echo $argv[2])
+    command cp -r $from $to
+else
+    command cp $argv
+end