docs: add devices readme

devices/README.md

@@ -0,0 +1,38 @@
+# Devices
+
+This directory encompasses every device's main configuration file.
+
+## List of my Devices
+
+| Name       | Description                                                                                             |
+| ---------- | ------------------------------------------------------------------------------------------------------- |
+| `android`  | My [Nix-On-Droid](https://github.com/nix-community/nix-on-droid) configuration for my OnePlus 9 Pro |
+| `binto`    | My desktop PC with a multi-monitor setup and an NVIDIA (cringe) 3070 |
+| `cluster`  | WIP |
+| `oksys`    | A very old Acer laptop that went from sailing the seas for years to becoming my web server and VPN host |
+| `servivi`  | A gaming PC in a previous life, it is now used to slowly convert my Proxmox server to NixOS |
+| `wim`      | My 2-1 Lenovo Laptop that I use for uni |
+
+## Global Vars
+
+In every device's `default.nix`, you'll find these [settings](../common/vars.nix)
+
+```nix
+# $FLAKE/devices/<name>/default.nix
+
+vars = {
+  mainUser = "matt";
+  hostName = "wim";
+  ...
+};
+```
+
+from these declared settings, I get access to global variables
+that are different on each host using a 'let in' block:
+
+```nix
+let
+  inherit (config.vars) mainUser ...;
+in {
+  ...
+```