Document --host and --port flag for preview (#9572)

Author: bluwy

.changeset/sixty-bugs-unite.md

@@ -0,0 +1,5 @@
+---
+"astro": patch
+---
+
+Documents supported `--host` and `--port` flags in `astro preview --help`

packages/astro/src/cli/preview/index.ts

@@ -15,6 +15,9 @@ export async function preview({ flags }: PreviewOptions) {
 			usage: '[...flags]',
 			tables: {
 				Flags: [
+					['--port', `Specify which port to run on. Defaults to 4321.`],
+					['--host', `Listen on all addresses, including LAN and public addresses.`],
+					['--host <custom-address>', `Expose on a network IP address at <custom-address>`],
 					['--open', 'Automatically open the app in the browser on server start'],
 					['--help (-h)', 'See all available flags.'],
 				],