Add ledger-cli.org to sites.yml

[afh]

Thanks for the review and approval, @tdreyno. Am I correct in assuming that the failing checks are unrelated to the changes in this proposed PR?

[tdreyno]

@afh they are unrelated. looks like the hosting service has changed something. however, they will cause this change to not deploy so I need to fix it before merging

[afh]

Thanks for the info and added context, @tdreyno. Hoping that fixing whatever changed with the hosting services isn't too much of a hassle 🤞

[afh]

🙅 Please hold as the PR ledger/ledger.github.io#73 moves the project away from middleman. I'll close this issue once the PR is merged.