Feat/add spdx headers

[vitormattos]

• Created a tool to update all headers: https://github.com/LibreCodeCoop/spdx-header-updater
• Add headers to remaining files
• Add status badge
  • Add LibreSign to https://api.reuse.software/info/github.com/LibreSign/libresign
• Add GH action to check for compliance on future changes
• Add pending license files

[vitormattos]

[vitormattos]

/backport to stable30

[backportbot-libresign]

The backport to stable30 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable30
git pull origin stable30

# Create the new backport branch
git checkout -b backport/3830/stable30

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick c1631457 6ab29c0a f9ea8e1c

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/3830/stable30

Error: Failed to push branch backport/3830/stable30: To https://github.com/LibreSign/libresign.git
! [remote rejected] backport/3830/stable30 -> backport/3830/stable30 (refusing to allow a GitHub App to create or update workflow .github/workflows/update-psalm-baseline.yml without workflows permission)
error: failed to push some refs to 'https://github.com/LibreSign/libresign.git'

---

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

[vitormattos]

/backport to stable30

[backportbot-libresign]

The backport to stable30 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable30
git pull origin stable30

# Create the new backport branch
git checkout -b backport/3830/stable30

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick c1631457 6ab29c0a f9ea8e1c

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/3830/stable30

Error: Failed to push branch backport/3830/stable30: To https://github.com/LibreSign/libresign.git
! [remote rejected] backport/3830/stable30 -> backport/3830/stable30 (refusing to allow a GitHub App to create or update workflow .github/workflows/update-psalm-baseline.yml without workflows permission)
error: failed to push some refs to 'https://github.com/LibreSign/libresign.git'

---

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

[vitormattos]

/backport to stable29

[vitormattos]

/backport to stable28

[backportbot-libresign]

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/3830/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 c1631457 6ab29c0a f9ea8e1c

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/3830/stable29

Error: Failed to push branch backport/3830/stable29: To https://github.com/LibreSign/libresign.git
! [remote rejected] backport/3830/stable29 -> backport/3830/stable29 (refusing to allow a GitHub App to create or update workflow .github/workflows/behat-mariadb.yml without workflows permission)
error: failed to push some refs to 'https://github.com/LibreSign/libresign.git'

---

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