mechanic: use upstream's exponential level curve

tests/test_mechanic.py

@@ -0,0 +1,9 @@
+from pqcli.mechanic import level_up_time
+
+
+def test_level_up_time_matches_upstream() -> None:
+    # Math.round((20 + Math.pow(1.15, level)) * 60), pq-web 5cd39f1
+    assert level_up_time(1) == 1269
+    assert level_up_time(10) == 1443
+    assert level_up_time(30) == 5173
+    assert level_up_time(100) == 70460007