Added Seafile folder and configuration files

[airfrog7]

Seattle: New Service

Description

Added Seafile folder, ReadMe.md, Compose.yaml and .env files.

Related Issues

• None.

Verification

I deployed the stack to a couple of different Docker instances and both worked as expected. The Seafile website is accessible via a web browser and I can log in to the desktop and mobile clients to download and upload files.

Checklist

• I have performed a self-review of my code and followed the templates structure.
• I have added verification that the stack works as expected.
• I have updated necessary documentation (e.g. frontpage README.md ).
• I have selected the correct label(s) for this PR.

Additional Context

• I don't have access to add a label, but "New Service" would be appropriate.
• A couple of times when I deployed this stack (via Portainer) I got a timeout error. However, everything still deployed successfully after a few minutes. This is probably more due to my under-powered hardware than Docker or the Seafile components.