doc: update the dev doc

.vscode/settings.json

@@ -6,6 +6,7 @@
     "clientgpversion",
     "clientos",
     "gpcommon",
+    "gpgui",
     "gpservice",
     "Immer",
     "jnlp",

README.md

@@ -1,8 +1,24 @@
 ## Development
 
+### Build the service
+
+```sh
+# Build the client first
+cargo build -p gpclient
+
+# Build the service
+cargo build -p gpservice
+```
+
+### Start the service
+
+```sh
+sudo ./target/debug/gpservice
+```
+
 ### Start the GUI
 
-```
+```sh
 cd gpgui
 pnpm install
 pnpm tauri dev