Add README and make some sanity changes.

README.md

@@ -0,0 +1,30 @@
+# DNSControl Configuration
+
+## Overview
+
+| Domain         | Purpose                        |
+|----------------|--------------------------------|
+| `arirex.me`    | Primary domain                 |
+| `achl.fr`      | Legacy domain                  |
+| `arirex.email` | Email proxy for primary domain |
+| `achlfr.email` | Email proxy for legacy domain  |
+
+## Usage
+
+```bash
+# Unlock credentials
+git-crypt unlock
+
+# Check planned changes
+dnscontrol preview
+
+# Apply DNS changes
+dnscontrol push
+```
+
+## Update
+
+```bash
+nix flake update
+dnscontrol write-types
+```