docs: add nilsreichardt as a contributor for security (#3488)

* docs: update README.md [skip ci]

* docs: update .all-contributorsrc [skip ci]

---------

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

.all-contributorsrc

@@ -3575,6 +3575,15 @@
       "contributions": [
         "doc"
       ]
+    },
+    {
+      "login": "nilsreichardt",
+      "name": "Nils Reichardt",
+      "avatar_url": "https://avatars.githubusercontent.com/u/24459435?v=4",
+      "profile": "https://github.com/nilsreichardt",
+      "contributions": [
+        "security"
+      ]
     }
   ],
   "contributorsPerLine": 6,