Merge Dependabot pull requests automatically

Currently, Dependabot detects vulnerable dependencies (CVE) and creates a security alert, with an associated pull request to update the dependency version.
These pull requests need to be approved and merged manually.
We want the Dependabot pull requests to be automatically approved and merged if all GitHub checks pass.

Moreover, we want to activate Dependabot version updates, to keep the packages we use updated to the latest versions. This will create pull requests regularly to bump dependencies, even though not detected as vulnerable.

The Dependabot pull requests:

• Will only affect minor or patch versions.
• Won't have any Jira issue in their Git commit, we can accept this rather than having to amend the commit message, etc.