docs: add schwalbe10 as a contributor for code, and review (#547)

* docs: update README.md [skip ci]

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

---------

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

Author: allcontributors[bot]

.all-contributorsrc

@@ -942,6 +942,16 @@
       "contributions": [
         "translation"
       ]
+    },
+    {
+      "login": "schwalbe10",
+      "name": "Kyohei Sahara",
+      "avatar_url": "https://avatars.githubusercontent.com/u/16644529?v=4",
+      "profile": "https://github.com/schwalbe10",
+      "contributions": [
+        "code",
+        "review"
+      ]
     }
   ],
   "contributorsPerLine": 7,