Set up nix develop to work with nix flakes

shell.nix

@@ -0,0 +1,25 @@
+{ pkgs ? import <nixpkgs> { } }:
+
+let
+  lib = pkgs.lib;
+in pkgs.mkShell rec {
+  name = "datasette";
+  buildInputs = with pkgs; [
+    sqlite
+    libspatialite
+    spatialite_tools
+    rlwrap
+
+    datasette
+  ];
+
+  LD_LIBRARY_PATH = "${lib.makeLibraryPath buildInputs}";
+
+  shellHook = ''
+    datasette \
+      --load-extension=mod_spatialite.so \
+      -m metadata.yml -h 0.0.0.0 --cors --setting default_cache_ttl 1800 \
+      --immutable dbs/*.db
+    datasette dbs/*
+  '';
+}