Move docs to mkdocs and improve them

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

docs/administration/CLI tasks/relay.md

@@ -0,0 +1,25 @@
+# Relay
+
+Manages remote relays
+
+## Make your instance follow a mobilizon instance
+
+```bash
+mix mobilizon.relay follow <relay_url>
+```
+
+Example: 
+```bash
+mix mobilizon.relay follow https://example.org/relay
+```
+
+## Make your instance unfollow a mobilizon instance
+
+```bash
+mix mobilizon.relay unfollow <relay_url>
+```
+
+Example: 
+```bash
+mix mobilizon.relay unfollow https://example.org/relay
+```