Moved scripts to the overlay folder to be used as packages

All scripts have been moved to the overlay folder in the top level directory

Overlay is now instantiated per configuration to make use of the host variable

overlay/scripts/commands/runbg.nix

@@ -0,0 +1,27 @@
+{ pkgs, }:
+pkgs.writeShellApplication {
+  name = "runbg";
+  runtimeInputs = with pkgs; [
+    coreutils # Provides `basename`, `which`, etc.
+    bash # Provides the Bash shell
+    util-linux # Provides `tty`
+  ];
+  text = ''
+    #!/usr/bin/env bash
+
+    [ $# -eq 0 ] && {  # $# is number of args
+        echo "$(basename "$0"): missing command" >&2
+        exit 1
+    }
+    prog="$(which "$1")"  # see below
+    [ -z "$prog" ] && {
+        echo "$(basename "$0"): unknown command: $1" >&2
+        exit 1
+    }
+    shift  # remove $1, now $prog, from args
+    tty -s && exec </dev/null      # if stdin is a terminal, redirect from null
+    tty -s <&1 && exec >/dev/null  # if stdout is a terminal, redirect to null
+    tty -s <&2 && exec 2>&1        # stderr to stdout (which might not be null)
+    "$prog" "$@" &  # $@ is all args
+  '';
+}