minor #19263 [Mailer] Mention webhook support in Mailer bridge overview (OskarStark)

This PR was squashed before being merged into the 6.3 branch.

Discussion
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[Mailer] Mention webhook support in Mailer bridge overview

Refs
* #19249

cc `@MrYamous` `@TimoBakx`

What do you think about this?

Do we have other bridges which supporting webhook since 6.3 ? 🤔

Commits
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d8c2c3b [Mailer] Mention webhook support in Mailer bridge overview

Author: OskarStark

mailer.rst

@@ -99,20 +99,20 @@ Using a 3rd Party Transport
 Instead of using your own SMTP server or sendmail binary, you can send emails
 via a third-party provider:
 
-===================== ===============================================
-Service               Install with
-===================== ===============================================
+===================== =============================================== ===============
+Service               Install with                                    Webhook support
+===================== =============================================== ===============
 `Amazon SES`_         ``composer require symfony/amazon-mailer``
 `Infobip`_            ``composer require symfony/infobip-mailer``
-`Mailgun`_            ``composer require symfony/mailgun-mailer``
+`Mailgun`_            ``composer require symfony/mailgun-mailer``     yes
 `Mailjet`_            ``composer require symfony/mailjet-mailer``
 `MailPace`_           ``composer require symfony/mail-pace-mailer``
 `MailerSend`_         ``composer require symfony/mailer-send-mailer``
 `Mandrill`_           ``composer require symfony/mailchimp-mailer``
-`Postmark`_           ``composer require symfony/postmark-mailer``
+`Postmark`_           ``composer require symfony/postmark-mailer``    yes
 `SendGrid`_           ``composer require symfony/sendgrid-mailer``
 `Sendinblue`_         ``composer require symfony/sendinblue-mailer``
-===================== ===============================================
+===================== =============================================== ===============
 
 .. versionadded:: 6.2