Add missing optional dependency to web feature (#3805)

The 'web' feature in Cargo.toml listed `dioxus-web` as a dependency but
it also needed to have `dioxus/web` in order to compile properly.

examples/fullstack-auth/Cargo.toml

@@ -57,4 +57,4 @@ server = [
     "http",
     "tower",
 ]
-web = ["dioxus-web"]
+web = ["dioxus/web", "dioxus-web"]