feat(external-sites): add 0.3.1 to the marketplace

[LukasHirt]

Submit to the ownCloud marketplace

What are you submitting?

• An app (ownCloud Classic app)
• An oCIS web extension
• A publisher page

---

oCIS web extension

A web extension adds a release directory whose metadata is authored in
extension.yaml (oCIS reads it from the repository feed, not the bundle).

• Extension id (the reverse-DNS id in extension.yaml): com.github.owncloud.web-extensions.external-sites
• Folder slug (<ext-id>, also the release tag / asset name): external-sites
• Version (the version in extension.yaml): 0.3.1
• Files added: extensions/external-sites/releases/0.3.1/ containing bundle.zip
  (Git LFS) and extension.yaml and a screenshots/ dir.

Checklist

• bundle.zip and extension.yaml are committed under extensions/external-sites/releases/0.3.1/.
• The version in extension.yaml matches the releases/<version>/ directory name.
• The reverse-DNS id is the same across every release of this extension.
• This is a new release — I am not modifying or deleting an already-published release.
• extension.yaml has at least one authors entry and at least one tags entry.

Built from web-extensions release external-sites-v0.3.1, reviewed locally via extctl publish before approval.

_{🤖 Generated by extctl publish}

[LukasHirt]

Thanks for the review — this has been updated in place on the same branch (amended commit, force-pushed), not regenerated:

• name / subtitle: restored to the curated values already published for this extension (no longer the generator's title-cased slug / upstream package.json description).
• cover: cover: true + cover.png added at the release root, matching the cover art already live for this extension.
• Git LFS: bundle.zip and the screenshots are now committed as real LFS pointers (content byte-identical to before — same hash you already sha256-verified).
• minOCIS: 7.0.0 — verified by actually running this release's own e2e test against real owncloud/ocis Docker images (not the previous carried-forward guess).

Ready for another look whenever you have time.