feat: support excalidraw file

[hweihwang]

Summary

• Support new excalidraw file type

[blizzz]

would be an opportunity to add return type hint here and in updateMimetypes()

[github-actions]

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[juliushaertl]

Tests needs some adjustment it seems:

1. Test\IntegrityCheck\CheckerTest::testVerifyCoreSignatureWithModifiedMimetypelistSignatureData

[juliushaertl]

@hweihwang Pushed a small commit to adjust the icon color to match the others.

[juliushaertl]

Looks good, cypress seems unrelated, could you squash your commits and rebase to latest master afterwards? Will push my icon fix again then afterwards.

[juliushaertl]

@hweihwang Had another conflict in the mean time, could you check?

[welcome]

Thanks for your first pull request and welcome to the community! Feel free to keep them coming! If you are looking for issues to tackle then have a look at this selection: https://github.com/nextcloud/server/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22

[juliushaertl]

/backport to stable29

[juliushaertl]

/backport to stable28

[backportbot]

The backport to stable29 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable29
git pull origin stable29

# Create the new backport branch
git checkout -b backport/45353/stable29

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick 9a2f026b f5fbe435

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/45353/stable29

Error: No changes found in backport branch

---

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

[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/45353/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 9a2f026b f5fbe435

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/45353/stable28

Error: No changes found in backport branch

---

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