feature: add support for S21 Hydro (#283)

docs/miners/antminer/X21.md

@@ -14,6 +14,19 @@
         show_root_heading: false
         heading_level: 0
 
+## S21 Hydro (Stock)
+
+- [x] Shutdowns
+- [x] Power Modes
+- [ ] Setpoints
+- [ ] Presets
+
+::: pyasic.miners.antminer.bmminer.X21.S21.BMMinerS21Hydro
+    handler: python
+    options:
+        show_root_heading: false
+        heading_level: 0
+
 ## S21 Pro (Stock)
 
 - [x] Shutdowns

docs/miners/supported_types.md

@@ -105,6 +105,7 @@ details {
                     <li><a href="../antminer/X21#s21-stock">S21 (Stock)</a></li>
                     <li><a href="../antminer/X21#s21-pro-stock">S21 Pro (Stock)</a></li>
                     <li><a href="../antminer/X21#t21-stock">T21 (Stock)</a></li>
+                    <li><a href="../antminer/X21#s21-hydro-stock">S21 Hydro (Stock)</a></li>
                 </ul>
         </details>
     </ul>