docs: add commands

docs/cli/src/cmd/serve.md

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+# Serve
+
+`dioxsu serve` can start a dev server (include hot-reload tool) to run the project.
+
+```
+dioxus-serve 
+Build, watch & serve the Rust WASM app and all of its assets
+
+USAGE:
+    dioxus serve [OPTIONS]
+
+OPTIONS:
+        --example <EXAMPLE>      [default: ""]
+        --platform <PLATFORM>    [default: "default_platform"]
+        --release                [default: false]
+```
+
+you can use this command to build project and start a `dev server` :
+
+```
+dioxus serve
+```
+
+## Target platform
+
+use option `platform` choose build target platform:
+
+```
+# for desktop project
+dioxus serve --platform desktop
+```
+
+`platform` only supports `desktop` & `web`.
+
+`dev-server` only for `web` project.
+
+```
+# for web project
+dioxus serve --platform web
+```
+
+## Serve Example
+
+you can use `--example {name}` to start a example code.
+
+```
+# build `example/test` code
+dioxus serve --exmaple test
+```