Feat: add --open to deno serve to open server in browser

[marvinhagemeister]

Most dev servers allow you to pass --open to open the page automatically in the browser. It's a neat minor DX enhancement compared to having to click the link yourself.

When passing deno serve --open the browser should open the address where the server is running on. Vite goes a bit the extra mile to ensure that the same tab is re-used via some apple script vodoo https://github.com/vitejs/vite/blob/561b940f6f963fbb78058a6e23b4adad53a2edb9/packages/vite/src/node/server/openBrowser.ts#L71-L141

[bartlomieju]

No strong feeling either way, seems like a cool feature.

We already have a dependency crate that handles opening the browser, an example usage is here:

deno/cli/tools/registry/mod.rs

Lines 602 to 603 in e7026c5

	log::info!("{}", colors::gray("Waiting..."));
	let _ = open::that_detached(&auth_url);

[HasanAlrimawi]

I'm working on it if still possible.
I've done half the way (supported the --open, also added it to ServeFlags, as well as opened browser based on the host and port found at least made sure it works for localhost, it should work for servers too ).
Just trying to figure out how to only open the browser on success of the deno serve, since sometimes the deno serve shows error and the site shows unreachable message.