docs: add douglasparker as a contributor (#802) [skip ci]

* 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

@@ -292,6 +292,15 @@
       "contributions": [
         "code"
       ]
+    },
+    {
+      "login": "douglasparker",
+      "name": "Douglas Parker",
+      "avatar_url": "https://avatars.githubusercontent.com/u/18235822?v=4",
+      "profile": "https://www.douglas-parker.com",
+      "contributions": [
+        "doc"
+      ]
     }
   ],
   "badgeTemplate": "<a href=\"#contributors-\"><img alt=\"All Contributors\" src=\"https://img.shields.io/badge/all_contributors-<%= contributors.length %>-orange.svg\"/></a>",