docs/config.md: Fix typo, provide an example key with camelCase and where to find more

[ci skip]

docs/config.md

@@ -110,9 +110,9 @@ Frontends can access these settings at `/api/pleroma/frontend_configurations`
 
 To add your own configuration for PleromaFE, use it like this:
 
-`config :pleroma, :frontend_configurations, :pleroma_fe, %{theme: "my-theme", ...}`
+`config :pleroma, :frontend_configurations, :pleroma_fe: %{redirectRootNoLogin: "/main/all", ...}`
 
-These settings need to be complete, they will overide the defaults.
+These settings need to be complete, they will override the defaults. See `priv/static/static/config.json` for the available keys.
 
 ## :fe
 __THIS IS DEPRECATED__