Update fsdocs

Author: brianrourkeboll

.config/dotnet-tools.json

@@ -3,11 +3,11 @@
   "isRoot": true,
   "tools": {
     "fsdocs-tool": {
-      "version": "20.0.0",
+      "version": "21.0.0-beta-001",
       "commands": [
         "fsdocs"
       ],
       "rollForward": false
     }
   }
-}
+}