Datetime: Tidy up docs (GH-144720)

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

Author: StanFromIreland

.github/CODEOWNERS

@@ -424,6 +424,7 @@ Lib/test/test_dataclasses/    @ericvsmith
 
 # Dates and times
 Doc/**/*time.rst                 @pganssle @abalkin
+Doc/library/datetime-*           @pganssle
 Doc/library/zoneinfo.rst         @pganssle
 Include/datetime.h               @pganssle @abalkin
 Include/internal/pycore_time.h   @pganssle @abalkin

Doc/library/datetime-inheritance.dot

@@ -0,0 +1,31 @@
+// Used to generate datetime-inheritance.svg with Graphviz
+// (https://graphviz.org/) for the datetime documentation.
+
+digraph {
+    comment="Generated with datetime-inheritance.dot"
+    graph [
+        bgcolor="transparent"
+        fontnames="svg"
+        layout="dot"
+        ranksep=0.5
+        nodesep=0.5
+        splines=line
+    ]
+    node [
+        fontname="Courier"
+        fontsize=14.0
+        shape=box
+        style=rounded
+        margin="0.15,0.07"
+    ]
+    edge [
+        arrowhead=none
+    ]
+
+    object -> tzinfo
+    object -> timedelta
+    object -> time
+    object -> date
+    tzinfo -> timezone
+    date -> datetime
+}