feat(cli): support custom devServer port

packages/vant-cli/src/compiler/compile-site.ts

@@ -13,7 +13,7 @@ function watch() {
 
   getPort(
     {
-      port: 8080
+      port: siteDevConfig.devServer!.port
     },
     (err, port) => {
       if (err) {

packages/vant-cli/src/config/webpack.site.dev.ts

@@ -44,6 +44,7 @@ export const siteDevBaseConfig = merge(baseConfig as any, {
     'site-mobile': [join(__dirname, '../../site/mobile/main.js')]
   },
   devServer: {
+    port: 8080,
     quiet: true,
     host: '0.0.0.0',
     stats: 'errors-only',