Add `ard_*()` function for `stats::poisson.test()` #304

All 72 tests pass, 33 skipped in 59s

1 files ± 0 105 suites +1 59s ⏱️ -3s
105 tests + 1 72 ✅ - 32 33 💤 +33 0 ❌ ±0
500 runs - 81 455 ✅ - 126 45 💤 +45 0 ❌ ±0

Results for commit d38cc2e. ± Comparison against earlier commit 257c585.