feat: README

README.md

···
+# Config
+
+It only contains a Home Manager config because the purpose is to run Nix inside a Fedora Toolbox.
+
+Here are the commands to set it up:
+
+```bash
+sudo dnf install nix --exclude nix-daemon
+sudo usermod -aG nixbld $USER
+```
+
+Restart your toolbox session to apply the group change, then run:
+
+```bash
+nix run nixpks#home-manager switch --flake .
+```