docs: Update QuickStart.md

Add some documentation missing from the quickstart in how to actually login to the app.

QuickStart.md

@@ -50,6 +50,20 @@ npm run build
 npm run dev # note: you'll need to run build before every dev
 ```
 
+## First Login
+With the default configuration, Gram will be configured to use login via email. 
+
+For your first login, use the email address `admin@localhost`. 
+
+Since SMTP is not configured yet, you will need to get the actual link from your application logs:
+```
+[2023-11-07T14:29:12.229] [DEBUG] MagicLinkIdentityProvider - Sending magic link to <REDACTED> with link http://localhost:4726/login/callback/magic-link?token=<REDACTED>
+```
+
+For the default configuration, the login is limited to three hardcoded users: `user@localhost`, `reviewer@localhost` and `admin@localhost`.
+You will need to change the configuration to change this.
+
+
 ## Modify the configuration
 
 The `config/` package contains the configuration of your Gram application. This is where