Add Dependabot configuration for github-actions

[ghost]

This is a Minder automated pull request.

This pull request adds a Dependabot configuration to the repository to handle
package updates for github-actions.

For more information, see
https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file

[ggadt]

I created a PR for solving the linting error: #3412
If you merge that and rebase the repo, the error will be gone