elaborate on NixOS

Author: leo60228

README.md

@@ -4,7 +4,7 @@
 Building is done via scripts defined in the package.json.
 
 ### Requirements
-Development was done on NixOS 20.09. A `flake.nix` is provided, allowing for replication of the exact build environment. Alternatively, the following versions can be installed:
+Development was done on [NixOS](https://nixos.org) 20.09. A `flake.nix` is provided, allowing for replication of the exact build environment. Nix flakes are currently a WIP feature and not fully documented, so you may want to instead install the system dependencies manually:
 
 * Node.js 14.9.0 ([downloads](https://nodejs.org/download/release/v14.9.0/), [installation](https://github.com/nodejs/help/wiki/Installation))
 * Yarn 1.22.5 ([installation](https://classic.yarnpkg.com/en/docs/install/))