feat: Add Mailpit application (SMTP testing server with web UI)

[patou]

Mailpit is a modern email testing tool. It provides an SMTP server to capture outgoing emails and a web UI to inspect messages, headers and attachments.

Features

• Web UI to browse and inspect captured emails
• SMTP endpoint for application testing
• Persistent local database for captured messages
• Reverse-proxied web access through YunoHost (domain/path)

[orhtej2]

!invite @patou

[yunohost-bot]

@patou, you have just been invited to the YunoHost-Apps organization.
We suggest that you transfer your repository in the org so that you can take advantage of the automated CI tests and other packagers' help:

1. check your notifications and accept the invitation.
2. transfer your repository to the YunoHost-Apps organization.
3. open a PR from the testing branch to the main branch of your repository
4. add your commits and open a pull request.
5. trigger the CI with !testme in a comment in that PR.

Do not forget to update your repository URL in the catalog.

You can find more information on packaging in our documentation

[patou]

@orhtej2 thanks for your review I'm move the repository and update the PR.

[orhtej2]

Consider addressing linter warnings fro https://ci-apps-dev.yunohost.org/ci/job/22570

current lvl is 6, with warnings fixed 7/8, job only failed because the app is not yet in the catalog