Release v0.21.0

What's Changed

• chore: publish docker by @cfabianski in #312
• chore: use qemu to release by @cfabianski in #313
• feat: Do not visit Git-ignored files by @spdawson in #309
• docs: update datatype generation to handle parents by @markmichon in #307
• chore: separate publish and release process by @cfabianski in #314
• feat: Use encrypted_ column prefix to mark SQL detections encrypted by @spdawson in #302
• fix: keep existing release by @cfabianski in #320

Full Changelog: v0.20.1...v0.21.0