datetime types docs added (#431)

* datetime types docs added

* datetime docs format changed

docs/examples/datetime.py

@@ -0,0 +1,22 @@
+from datetime import date, datetime, time, timedelta
+from pydantic import BaseModel
+
+class Model(BaseModel):
+    d: date = None
+    dt: datetime = None
+    t: time = None
+    td: timedelta = None
+
+
+m = Model(
+    d=1966280412345.6789,
+    dt='2032-04-23T10:20:30.400+02:30',
+    t=time(4, 8, 16),
+    td='P3DT12H30M5S'
+)
+
+print(m.dict())
+# > {'d': datetime.date(2032, 4, 22),
+# 'dt': datetime.datetime(2032, 4, 23, 10, 20, 30, 400000, tzinfo=datetime.timezone(datetime.timedelta(seconds=9000))),
+# 't': datetime.time(4, 8, 16),
+# 'td': datetime.timedelta(days=3, seconds=45005)}