Add docker files to run nix dev environment on Windows

nix/Dockerfile

@@ -0,0 +1,22 @@
+# This Dockerfile is only used as a development environment for
+# non-nix systems, i.e. Windows.
+
+FROM nixos/nix:latest
+
+RUN apk --no-cache add \
+    wget
+
+RUN nix-env -iA cachix -f https://cachix.org/api/v1/install \
+ && cachix use postgrest
+
+# We need an unprivileged user here, to make PG run at all.
+RUN adduser --disabled-password --ingroup root nix \
+ && chown -R nix:root /nix
+USER nix:root
+ENV USER=nix
+
+VOLUME /nix
+VOLUME /postgrest
+WORKDIR /postgrest
+
+CMD nix-shell