docs: add hydrargyrum as a contributor (#839)

Co-authored-by: allcontributors[bot] <46447321+allcontributors[bot]@users.noreply.github.com>

.all-contributorsrc

@@ -730,6 +730,15 @@
       "contributions": [
         "doc"
       ]
+    },
+    {
+      "login": "hydrargyrum",
+      "name": "hydrargyrum",
+      "avatar_url": "https://avatars.githubusercontent.com/u/2804645?v=4",
+      "profile": "https://indigo.re/",
+      "contributions": [
+        "doc"
+      ]
     }
   ],
   "contributorsPerLine": 7,

README.md

@@ -142,6 +142,7 @@ Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/d
   </tr>
   <tr>
     <td align="center"><a href="https://nymous.io"><img src="https://avatars1.githubusercontent.com/u/4216559?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Thomas Gaudin</b></sub></a><br /><a href="https://github.com/containrrr/watchtower/commits?author=nymous" title="Documentation">📖</a></td>
+    <td align="center"><a href="https://indigo.re/"><img src="https://avatars.githubusercontent.com/u/2804645?v=4?s=100" width="100px;" alt=""/><br /><sub><b>hydrargyrum</b></sub></a><br /><a href="https://github.com/containrrr/watchtower/commits?author=hydrargyrum" title="Documentation">📖</a></td>
   </tr>
 </table>