Link to commits in PG 10 release notes

Hi,

I wonder if there's a reasonable way that allows to add links to the
more crucial commits for changelog entries. The source e.g. has

<listitem>
<!--
Author: Robert Haas <rhaas(at)postgresql(dot)org>
2017-03-08 [98e6e8904] tidbitmap: Support shared iteration.
Author: Robert Haas <rhaas(at)postgresql(dot)org>
2017-03-08 [f35742ccb] Support parallel bitmap heap scans.
-->
<para>
Support parallel bitmap heap scans (Dilip Kumar)
</para>

<para>
This allows a single index scan to dispatch parallel workers to process
different areas of the heap.
</para>
</listitem>

for an item, and it'd be pretty cool if we could have a link to those
two commits from the entry. It'd need be pretty unobstrusive to avoid
making things hard to read, but it'd obviate some of the need to list
details, and it gives curious people changes to see what actually
changed.

- Andres