docs(README): more documentation on IPv6 (#152)

* docs(README): more documentation on IPv6

* docs(README): streamline the instructions on IPv6

* docs(README): minor tweaks

README.markdown

@@ -112,9 +112,24 @@ services:
 ```
 
 <details>
-<summary>📡 Use <code>network_mode: host</code> (as a hack) to enable IPv6 or read more.</summary>
-
-The setting `network_mode: host` is for IPv6. If you wish to keep the network separated from the host network, check out the [proper way to enable IPv6 support](https://docs.docker.com/config/daemon/ipv6/) and [this GitHub issue about using IPv6 in Docker.](https://github.com/favonia/cloudflare-ddns/issues/119)
+<summary>📡 Use <code>network_mode: host</code> to enable IPv6 (or read more).</summary>
+
+The easiest way to enable IPv6 is to use `network_mode: host` so that the tool can access the host IPv6 network directly. If you wish to keep the tool isolated from the host network, check out the [official documentation on IPv6](https://docs.docker.com/config/daemon/ipv6/) and [this GitHub issue about IPv6.](https://github.com/favonia/cloudflare-ddns/issues/119) If your host OS is Linux, here’s the tl;dr:
+
+1. Use `network_mode: bridge` instead of `network_mode: host`.
+2. Edit or create `/etc/docker/daemon.json` with the following content:
+   ```json
+   {
+     "ipv6": true,
+     "fixed-cidr-v6": "fd00::/8",
+     "experimental": true,
+     "ip6tables": true
+   }
+   ```
+3. Restart the Docker daemon (if you are using systemd):
+   ```sh
+   systemctl restart docker.service
+   ```
 </details>
 
 <details>