Ignore unused arguments prefixed with an underscore

[zimeg]

Type of change

• [ ] New sample
• [ ] New feature
• [x] Bug fix
• [ ] Documentation

Summary

This PR adds a condition to the no-unused-vars linter rule to ignore errors for variables prefixed with an underscore.

Unfortunately the args-after-used option doesn't apply to object parameters, so this is the best workaround I can think of. Open to other suggestions of course!

Notes

• I'm hoping this _client remains clear that it corresponds to the commented client. But not so sure about this...

Requirements

• [x] I’ve checked my submission against the Samples Checklist to ensure it complies with all standards
• [x] I have ensured the changes I am contributing align with existing patterns and have tested and linted my code
• [x] I've read and agree to the Code of Conduct

[zimeg]

There is a better solution. I believe it.