Add a direct link to perldelta in the release announcement

As the release announcement itself only contains the SHA1 digests and
not much information on the changes with this release, providing
a direct link to where the information is available seems to be wanted.

Porting/release_announcement_template.txt

@@ -17,7 +17,9 @@ SHA1 digests for this release are:
  [TAR.XZ SHA1]   perl-5.[VERSION.SUBVERSION].tar.xz
 
 You can find a full list of changes in the file "perldelta.pod" located in
-the "pod" directory inside the release and on the web.
+the "pod" directory inside the release and on the web at
+
+https://metacpan.org/pod/release/[AUTHOR]/perl-5.[VERSION.SUBVERSION]/pod/perldelta.pod
 
 [ACKNOWLEDGEMENTS SECTION FROM PERLDELTA]