Add CI workflow to check for unapproved Go dependency licenses

[per1234]

Please check if the PR fulfills these requirements

• [x] The PR has no duplicates (please search among the Pull Requests before creating one)
• [x] The PR follows our contributing guidelines
• [x] Tests for the changes have been added (for bug fixes / features)

What kind of change does this PR introduce?

Infrastructure enhancement

What is the current behavior?

Contributors and maintainers are not provided with any tools to assist them in the complex and esoteric subject of open source licence compliance.

What is the new behavior?

A task and GitHub Actions workflow are provided here for checking the license types of Go project dependencies.

On every push and pull request that affects relevant files, the CI workflow will use Licensed to check:

• If the dependency licenses cache is up to date
• If any of the project's dependencies have an unapproved license type.

Approval can be based on:

• Allowed license type
• Individual dependency

Other information

The workflow run is currently failing. This is an accurate result which is caused by incompatibility of the Apache 2.0 license of the Arduino Language Server with the license of dependencies used by the project, which underscores the need for the system added here.

Resolution of that non-compliance is out of scope for this PR.