JSON Output for Check Links Subcommand

[ohsh6o]

Hello, thank you for developing such a useful tool. I would like to evaluate this tool as part of my work project (see reference GSA/fedramp-automation#130). To move forward, I would like if the --check-links --json parameters could be combined to both check all referenced links and report the results per detected hyperlink in JSON.

If this project is still maintained, I can submit a pull request. If not, I can evaluate the feasibility of that in a fork.