docs: add flakeless examples; describe flakes prerequisites

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I6a6a6964c8369dbdf7366e333378ee25d125c707

docs/manual/installation/modules/flakes.md

@@ -0,0 +1,33 @@
+### Prerequisites {#sec-flakes-prerequisites}
+
+To install nvf with flakes, you must make sure the following requirements are
+met.
+
+1. Nix 2.4 or later must be installed. You may use `nix-shell` to get a later
+   version of Nix from nixpkgs.
+2. Flake-related experimental features must be enabled. Namely, you need
+   `nix-command` and `flakes`. Some Nix vendors enable those by default, please
+   consult their documentation if you are not using mainstream Nix.
+   - When using NixOS, add the following to your `configuration.nix` and rebuild
+     your system.
+
+     ```nix
+     nix.settings.experimental-features = "nix-command flakes";
+     ```
+
+   - If you are not using NixOS, add the following to `nix.conf` (located at
+     `~/.config/nix/` or `/etc/nix/nix.conf`).
+
+     ```bash
+     experimental-features = nix-command flakes
+     ```
+
+   - You may need to restart the Nix daemon with, for example,
+     `sudo systemctl restart nix-daemon.service`.
+
+   - Alternatively, you can enable flakes on a per-command basis with the
+     following additional flags to `nix` and `home-manager`:
+
+     ```sh
+     $ nix --extra-experimental-features "nix-command flakes" <sub-commands>
+     ```