Re-export the axum feature flag under "server" (#2786)

* re-export the axum feature flag under "server"
* remove the axum prefix from all the fullstack examples

packages/fullstack/examples/router/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "fullstack-router-example"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+dioxus = { workspace = true, features = ["fullstack", "router"] }
+axum = { workspace = true, optional = true }
+tokio = {workspace = true, features = ["full"], optional = true }
+serde = { version = "1.0.159", features = ["derive"] }
+
+[features]
+default = []
+server = ["axum", "dioxus/axum"]
+web = ["dioxus/web"]
+