fix: Add alt attribute to image nodes

[juliusknorr]

📝 Summary

It seems otherwise browser would read out the full URL with screen readers. We already have the alt text as user defined description for each image so we should make use of that.

[AndyScherzinger]

/backport to stable28

[backportbot]

The backport to stable28 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable28
git pull origin stable28
# Create the new backport branch
git checkout -b backport/5393/stable28
# Cherry pick the change from the commit sha1 of the change against the default branch# This might cause conflicts, resolve them
git cherry-pick 8a3c21a0
# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/5393/stable28

Error: Failed to clone repository: Failed to clone and cache repo: Cloning into '.'...
error: RPC failed; curl 92 HTTP/2 stream 5 was not closed cleanly: CANCEL (err 8)
error: 1410 bytes of body are still expected
fetch-pack: unexpected disconnect while reading sideband packet
fatal: early EOF
fatal: fetch-pack: invalid index-pack output

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Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.

[juliusknorr]

/backport to stable28

[susnux]

@juliushaertl maybe we should hide the span below (class="name") for a11y? meaning making it aria-hidden="true". Because it duplicates the alt tag.