fix(docs): update to react 18 and latest gatsby deps (#462)

Closes #216
Closes #230
Closes #460

---------

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: wolfy1339

docs/gatsby-config.js

@@ -87,7 +87,7 @@ module.exports = {
     {
       resolve: "gatsby-plugin-versioned-docs",
       options: {
-        currentVersion: "v20", // configure the path for the current version
+        currentVersion: "v21", // configure the path for the current version
         versions: [
           {
             name: "v16", // the path of the older version
@@ -109,6 +109,11 @@ module.exports = {
             branch: "19.x", // older versions specify a branch name for this repo
             endpoints: "7.x", // ...and one for the endpoint methods
           },
+          {
+            name: "v20", // the path of the older version
+            branch: "20.x", // older versions specify a branch name for this repo
+            endpoints: "10.x", // ...and one for the endpoint methods
+          },
         ],
       },
     },