Allow toggling `justMyCode` without settings.json

[nrbnlulu]

Usually I don't create settings.json files nor run configurations. it would be extremely helpful if
we could toggle justMyCode using a button 😊

[github-actions]

Thanks for the feature request! We are going to give the community 60 days from when this issue was created to provide 7 👍 upvotes on the opening comment to gauge general interest in this idea. If there's enough upvotes then we will consider this feature request in our future planning. If there's unfortunately not enough upvotes then we will close this issue.