Add Dactyl Manuform board (variants)

[dunk2k]

Add variants:

• 4x5
• 4x6
• 5x6
• 5x7
• 6x6
• 6x7

[dunk2k]

lease don't push every single commit individually to the PR. I've been away for a couple of days and have 70 notifications about incremental fixes; it got spammy after about 5. Additionally, if you know that a PR is "work in progress", mark it as a draft PR and only promote it to a reviewable PR once you're done

duly noted