Test CF-1.12-1

Test release 1

What's Changed

• Cf data model by @zklaus in #1
• Leap seconds by @davidhassell in #10
• Harmonised links to NUG by @larsbarring in #11

New Contributors

• @zklaus made their first contribution in #1
• @davidhassell made their first contribution in #10
• @larsbarring made their first contribution in #11

Full Changelog: https://github.com/davidhassell/cf-conventions/commits/CF-1.12-test-1