Read and write to /etc/hosts

TL;DR:
- Rename website-blocker to url-blocker
- Add a README.md
- Reads and writes to /etc/hosts

tools/url-blocker/shell.nix

@@ -0,0 +1,12 @@
+let
+  pkgs = import <unstable> {};
+in pkgs.mkShell {
+  buildInputs = with pkgs; [
+    (haskellPackages.ghcWithPackages (hpkgs: with hpkgs; [
+      time
+      aeson
+      either
+      hspec
+    ]))
+  ];
+}