docs: add jensim as a contributor (#336)

* 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

@@ -312,6 +312,15 @@
         "ideas",
         "maintenance"
       ]
+    },
+    {
+      "login": "jensim",
+      "name": "Jens",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/3663856?v=4",
+      "profile": "https://github.com/jensim",
+      "contributions": [
+        "doc"
+      ]
     }
   ],
   "contributorsPerLine": 8,