Add bt.TimeDelta and ht.timedelta converters #496

All 256 tests pass in 23s

10 files ±0 10 suites ±0 23s ⏱️ -4s
256 tests ±0 256 ✅ ±0 0 💤 ±0 0 ❌ ±0
2 510 runs ±0 2 510 ✅ ±0 0 💤 ±0 0 ❌ ±0

Results for commit df6558b. ± Comparison against earlier commit 29b711c.