docs: update the quickstart page (#16666)

## Changes
1. Update the `0.0.0.0:3001` web UI address to `localhost:3000`. Coder
starts on port 3000 by default. It'd use 3001 only if 3000 was already
taken.
2. Update the screenshot of the `/setup` page to reflect how it will
look like after merging #16662. Note:
this PR should be merged only after the other one is.
3. Minor phrasing changes.

---------

Co-authored-by: EdwardAngert <17991901+EdwardAngert@users.noreply.github.com>

Author: hugodutka

docs/images/screenshots/welcome-create-admin-user.png

@@ -82,18 +82,22 @@ persistent environment from your main device, a tablet, or your phone.
 
 ## Configure Coder with a new Workspace
 
-1. If you're running Coder locally, go to <http://0.0.0.0:3001/setup>.
+1. Coder will attempt to open the setup page in your browser. If it doesn't open
+   automatically, go to <http://localhost:3000>.
 
    - If you get a browser warning similar to `Secure Site Not Available`, you
      can ignore the warning and continue to the setup page.
 
-   If your Coder server is on a network or cloud device, locate the message in
-   your terminal that reads,
-   `View the Web UI: https://<CUSTOM-STRING>.<TUNNEL>.try.coder.app`. The server
-   begins to stream logs immediately and you might have to scroll up to find it.
+   If your Coder server is on a network or cloud device, or you are having
+   trouble viewing the page, locate the web UI URL in Coder logs in your
+   terminal. It looks like `https://<CUSTOM-STRING>.<TUNNEL>.try.coder.app`.
+   It's one of the first lines of output, so you might have to scroll up to find
+   it.
 
-1. On the **Welcome to Coder** page, enter the information to create an admin
-   user, then select **Create account**.
+1. On the **Welcome to Coder** page, to use your GitHub account to log in,
+   select **Continue with GitHub**.
+   You can also enter an email and password to create a new admin account on
+   the Coder deployment:
 
    ![Welcome to Coder - Create admin user](../images/screenshots/welcome-create-admin-user.png)_Welcome
    to Coder - Create admin user_